Circuit structure

ABSTRACT

A circuit structure includes a first busbar, a wiring board located on the first busbar and having an open hole, a conductive raised part protruding into the open hole from the first busbar, and a first electronic component having a first connection terminal located on the wiring board. The first connection terminal is electrically connected to the raised part in the open hole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage of PCT/JP2021/008631 filedon Mar. 5, 2021, which claims priority of Japanese Patent ApplicationNo. JP 2020-049132 filed on Mar. 19, 2020, the contents of which areincorporated herein.

TECHNICAL FIELD

The present disclosure relates to a circuit structure.

BACKGROUND

JP H9-321395A discloses a heat dissipation board on which electroniccomponents are installed.

The connection terminals of electronic components are tending to becomeshortener in length. Electrically connecting the connection terminals ofelectronic components to a busbar has thus become difficult. Thisproblem is more pronounced in the case of electronic components with aleadless package.

In view of this, an objective is to provide a technology that enables anelectronic component to be easily electrically connected to a busbar.

SUMMARY

A circuit structure of the present disclosure includes a first busbar, awiring board located on the first busbar and having an open hole, aconductive raised part protruding into the open hole from the firstbusbar, and a first electronic component having a first connectionterminal, the first connection terminal being electrically connected tothe raised part in the open hole.

Advantageous Effects

According to the present disclosure, a connection terminal of anelectronic component can be easily electrically connected to a busbar.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view showing an example of a circuitstructure.

FIG. 2 is a schematic plan view showing an example of the circuitstructure.

FIG. 3 is a schematic view showing an example of the cross-sectionalstructure of the circuit structure.

FIG. 4 is a schematic view showing an example of the cross-sectionalstructure of the circuit structure.

FIG. 5 is a schematic view showing an example of the cross-sectionalstructure of the circuit structure.

FIG. 6 is a schematic perspective view showing an example of theconfiguration of part of the circuit structure.

FIG. 7 is a schematic plan view showing an example of an electroniccomponent.

FIG. 8 is a schematic perspective view showing an example of a wiringboard.

FIG. 9 is a schematic perspective view showing an example of theconfiguration of part of the circuit structure.

FIG. 10 is a schematic perspective view for describing an example of amanufacturing method of the circuit structure.

FIG. 11 is a schematic perspective view for describing an example of themanufacturing method of the circuit structure.

FIG. 12 is a schematic perspective view for describing an example of themanufacturing method of the circuit structure.

FIG. 13 is a schematic perspective view for describing an example of themanufacturing method of the circuit structure.

FIG. 14 is a schematic perspective view for describing an example of themanufacturing method of the circuit structure.

FIG. 15 is a schematic perspective view for describing an example of amanufacturing method for an electrical junction box.

FIG. 16 is a schematic perspective view showing an example of anelectrical junction box.

FIG. 17 is a schematic perspective view showing an example of a circuitstructure.

FIG. 18 is a schematic plan view showing an example of the circuitstructure.

FIG. 19 is a schematic view showing an example of the cross-sectionalstructure of the circuit structure.

FIG. 20 is a schematic view showing an example of the cross-sectionalstructure of the circuit structure.

FIG. 21 is a schematic view showing an example of the cross-sectionalstructure of the circuit structure.

FIG. 22 is a schematic perspective view showing an example of theconfiguration of part of the circuit structure.

FIG. 23 is a schematic perspective view showing an example of theconfiguration of part of the circuit structure.

FIG. 24 is a schematic perspective view showing an example of theconfiguration of part of the circuit structure.

FIG. 25 is a schematic perspective view for describing an example of amanufacturing method of the circuit structure.

FIG. 26 is a schematic perspective view for describing an example of themanufacturing method of the circuit structure.

FIG. 27 is a schematic perspective view showing an example of anelectrical junction box.

FIG. 28 is a schematic view showing an example of the cross-sectionalstructure of the circuit structure.

FIG. 29 is a schematic view showing an example of the cross-sectionalstructure of the circuit structure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Initially, modes of the present disclosure will be enumerated anddescribed.

A circuit structure of the present disclosure is as follows.

The circuit structure includes a first busbar, a wiring board located onthe first busbar and having an open hole, a conductive raised partprotruding into the open hole from the first busbar, and a firstelectronic component having a first connection terminal, the firstconnection terminal being electrically connected to the raised part inthe open hole. According to the present disclosure, a conductive raisedpart protrudes from the first busbar into an open hole in the wiringboard. By electrically connecting the first connection terminal on thewiring board to the raised part in the open hole, the first connectionterminal can thus be easily electrically connected to the first busbar.

The raised part may be constituted by part of the first busbar. In thiscase, electrical resistance between the first connection terminal andthe first busbar can be reduced.

The first connection terminal may be bonded to the raised part. In thiscase, electrical resistance between the first connection terminal andthe first busbar can be reduced.

The wiring board may have a first land to which the first connectionterminal is bonded, and a conductive extension region extending from thefirst land and located around the open hole, and the circuit structuremay further include a conductive piece bonded to an upper surface of theraised part in the open hole and to the extension region. In this case,a conductive piece bonded to an extension region that extends from thefirst land to which the first connection terminal is bonded and islocated around the open hole and to the upper surface of the raised partin the open hole is provided. Due to this conductive piece, electricalresistance between the first connection terminal and the first busbarcan be reduced. Also, given that transfer of heat generated by the firstelectronic component to the first busbar is facilitated by theconductive piece, local increases in temperature tend not to occur.

The extension region may surround the open hole, and the conductivepiece may cover an opening edge of the open hole. In this case, thebonding area of the conductive piece with the extension region and theraised part can be increased. As a result, electrical resistance betweenthe first connection terminal and the first busbar can be furtherreduced.

The circuit structure may further include a second electronic componenthaving a second connection terminal located on the wiring board, thewiring board may further have a second land to which the secondconnection terminal is bonded, and the extension region may extend fromthe first land and the second land and be located around the open hole.In this case, given that the extension region to which the conductivepiece is bonded extends from both the first land to which the firstconnection terminal of the first electronic component is bonded and thesecond land to which the second connection terminal of the secondelectronic component is bonded and is located around the open hole, theextension region can be shared by the first electronic component and thesecond electronic component. Electrical resistance between the firstconnection terminal and the first busbar and electrical resistancebetween the second connection terminal and the first busbar can therebybe reduced with a simple configuration.

The circuit structure may further include a second busbar, the firstelectronic component may be provided to straddle between the wiringboard and the second busbar, and the wiring board may be located on aregion, on an upper surface of the first busbar, lower than an uppersurface of the second busbar. In this case, given that the wiring boardis located on a region of the upper surface of the first busbar that islower than the upper surface of the second busbar, a difference in levelbetween the wiring board and the second busbar can be suppressed.Therefore, providing the first electronic component to straddle betweenthe wiring board and the second busbar is facilitated.

The first busbar may be constituted by a cladding material.

Specific examples of a circuit structure of the present disclosure willbe described below with reference to the drawings. Note that the presentdisclosure is not limited to these illustrative examples and is definedby the claims, and all changes that come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

Embodiment 1 Outline of Circuit Structure

FIG. 1 is a schematic perspective view showing a circuit structure 1Aaccording to the present embodiment. The circuit structure 1A isincorporated in an electrical junction box 900 (see FIG. 16 below), forexample. The electrical junction box 900 is provided on a power supplypath between a battery and various electrical components in anautomobile, for example.

As shown in FIG. 1 , the circuit structure 1A includes an input-sidebusbar 2 (also simply referred to as busbar 2), an output-side busbar 3(also simply referred to as busbar 3), and an insulating member 4 forelectrically insulating the input-side busbar 2 and the output-sidebusbar 3. The circuit structure 1A further includes a wiring board 5, aplurality of electronic components 6, an electronic component 7, aconnector 8 and a plurality of conductive pieces 9.

The busbars 2 and 3 are conductive members. The electronic components 6are switching elements, for example. Specifically, the electroniccomponents 6 are MOSFETs (Metal-Oxide-Semiconductor Field-EffectTransistors), for example. A MOSFET is a type of semiconductor switchingelement. The electronic component 7 is a diode, for example.Specifically, the electronic component 7 is a Zener diode, for example.Hereafter, the electronic components 6 may be referred to as MOSFETs 6.The electronic component 7 may be referred to as Zener diode 7. Theelectronic components 6 may be switching elements other than MOSFETs.Also, the electronic components 6 may be electronic components otherthan switching elements. The electronic component 7 may be a diode otherthan a Zener diode. Also, the electronic component 7 may be anelectronic component other than a diode.

The drain terminals of the plurality of MOSFETs 6 are electricallyconnected to each other, for example. Also, the source terminals of theplurality of MOSFETs 6 are electrically connected to each other, forexample. The Zener diode 7 is an electronic component for preventing anovervoltage from being applied between the drain terminal and the sourceterminals of each MOSFET 6. A cathode terminal of the Zener diode 7 iselectrically connected to the drain terminals of the plurality ofMOSFETs 6, for example. An anode terminal of the Zener diode 7 iselectrically connected to the source terminals of the plurality ofMOSFETs 6, for example. The drain terminal of each MOSFET 6 iselectrically connected to the input-side busbar 2. The source terminalsof each MOSFET 6 is electrically connected to the output-side busbar 3.The drain terminals, source terminals and gate terminals of the MOSFET 6can also be said to be connection terminals. Similarly, the cathodeterminal and anode terminal of the Zener diode 7 can also be said to beconnection terminals. In the present example, the circuit structure 1Aincludes four MOSFETs 6, but the number of MOSFETs 6 included in thecircuit structure 1A is not limited thereto.

The busbar 2 is a plate-shaped metal member, for example. The busbar 2includes a main body part 20 and an input terminal part 21 protrudingfrom the main body part 20, for example. The main body part 20 and theinput terminal part 21 are located in the same plane. The main body part20 is a plate-shaped portion that is substantially L-shaped, forexample. The main body part 20 includes a first portion 201 and a secondportion 202 forming an L-shape with the first portion 201. The firstportion 201 and the second portion 202 are rectangular plate-shapedportions, for example. The drain terminal of each MOSFET 6 iselectrically connected to the first portion 201. The cathode terminal ofthe Zener diode 7 is electrically connected to the second portion 202.The input terminal part 21 is a plate-shaped portion and protrudes fromone longitudinal end of the second portion 202. The input terminal part21 has an open hole 210 that passes through in the thickness directionthereof. A wiring member extending from the battery is connected to theinput terminal part 21 by utilizing the open hole 210, for example. Abolt is, for example, passed through an open hole in a connectionterminal included in the wiring member and the open hole 210 of theinput terminal part 21, and a nut is then attached to the bolt, thusbolting the connection terminal of the wiring member to the inputterminal part 21. The output voltage of the battery is applied to theinput terminal part 21 through the wiring member. The output voltage ofthe battery applied to the input terminal part 21 is applied to thedrain terminals of the MOSFETs 6 through the main body part 20.

The busbar 3 is a plate-shaped metal member, for example. The busbars 2and 3 are located in the same plane. The busbar 3 includes a main bodypart 30 and an output terminal part 31 protruding from the main bodypart 30. The main body part 30 and the output terminal part 31 arelocated in the same plane. The main body part 30 is a rectangularplate-shaped portion, for example. The wiring board 5 is provided on themain body part 30. The main body part 30 is located in the same plane asthe main body part 20, so as to be adjacent to the first portion 201 andthe second portion 202 of the main body part 20. The long direction ofthe main body part 30 is parallel to the long direction of the firstportion 201. The source terminals of each MOSFET 6 and the anodeterminal of the Zener diode 7 are electrically connected to the mainbody part 30.

The output terminal part 31 is a plate-shaped portion and protrudes fromone end in the short direction of the main body part 30. The outputterminal part 31 is located in the same plane as the input terminal part21 so as to be adjacent thereto. The output terminal part 31 has an openhole 310 that passes through in the thickness direction thereof. Awiring member extending from an electrical component is connected to theoutput terminal part 31 by utilizing the open hole 310, for example,similarly to the input terminal part 21. The voltage that is output bythe source terminals of the MOSFETs 6 is applied to the output terminalpart 31. The voltage applied to the output terminal part 31 is appliedas a power supply to the electrical component through the wiring member,for example.

The insulating member 4 holds the busbars 2 and 3, while at the sametime electrically insulating the busbars 2 and 3. The insulating member4 is constituted by an insulating resin, for example. Specifically, theinsulating member 4 is constituted by PPS (Polyphenylene Sulfide) resin,for example. The insulating member 4 is molded as one piece with thebusbars 2 and 3, for example. The insulating member 4 is molded as onepiece with the busbars 2 and 3 by insert molding, for example. Theinsulating member 4 includes a frame-shaped insulating portion 41 and anL-shaped insulating portion 42 that is joined to the insulating portion41. The frame-shaped insulating portion 41 is attached to the main bodyparts 20 and 30 so as to surround the main body parts 20 and 30. TheL-shaped insulating portion 42 is located between the L-shaped main bodypart 20 and the main body part 30. The insulating portion 42 is locatedbetween the first portion 201 of the main body part 20 and the main bodypart 30, and is also located between the second portion 202 of the mainbody part 20 and the main body part 30. The busbars 2 and 3 areelectrically insulated by the insulating portion 42.

The wiring board 5 is a rectangular plate-shaped member, for example.The wiring board 5 is provided on the main body part 30 of the busbar 3.The wiring board 5 has an insulating board 50 and a conductive layer 51provided on the insulating board 50, for example. The insulating board50 may be a ceramic board or a board containing resin, for example. Inthe latter case, the insulating board 50 may be a glass epoxy board ormay be another board containing resin. The thickness of the insulatingboard 50 may be set from 0.4 mm to 0.6 mm inclusive, for example. Theconductive layer 51 may be constituted by copper or may be constitutedby another metal. The conductive layer 51 is provided on the uppersurface of the insulating board 50, for example. The wiring board 5 hasthe conductive layer 51 on the upper surface thereof. The wiring board 5may be a single-layer board or a multi-layer board. The wiring board 5may have a conductive layer on the lower surface or as an inner layer,in addition to the upper surface. The gate terminal of each MOSFET 6 iselectrically connected to the conductive layer 51 of the wiring board 5.In the present example, the wiring board is a rigid board, but may be asheet-like flexible board or a composite board in which a rigid boardand a flexible board are formed as one piece.

The connector 8 is provided on the upper surface of the wiring board 5.The gate terminals of the plurality of MOSFETs 6 are electricallyconnected to the connector 8 through the conductive layer 51 of thewiring board 5. Switching control of the MOSFETs 6 is performedexternally through the connector 8.

The plurality of conductive pieces 9 are provided in correspondence withthe plurality of MOSFETs 6. The conductive pieces 9 are each provided inorder to reduce electrical resistance between the source terminals ofthe MOSFET 6 corresponding thereto and the busbar 3. The conductivepieces 9 may be constituted by copper or another metal, for example. Inthe former case, the conductive pieces 9 may be constituted byoxygen-free copper, for example. Oxygen-free copper C1020 specified inJapanese Industrial Standards (JIS), for example, is employed as thisoxygen-free copper. The conductive pieces 9 may also be constituted by acopper alloy.

Detailed Description of Circuit Structure

FIG. 2 is a schematic plan view showing the circuit structure 1A. FIG. 3is a schematic view showing the cross-sectional structure taken along aline indicated by arrows A-A shown in FIG. 2 . FIG. 4 is a schematicview showing the cross-sectional structure taken along a line indicatedby arrows B-B shown in FIG. 2 . FIG. 5 is a schematic view showing thecross-sectional structure taken along a line indicated by arrows C-Cshown in FIG. 2 . FIG. 6 is a schematic perspective view showing anexample of the busbar 2, the busbar 3, the insulating member 4 and thewiring board 5 that are included in the circuit structure 1A. In FIG. 6, the wiring board 5 separated from the busbar 3 is shown.

Example Configuration of Busbar

The busbar 2 is constituted by a cladding material, for example. Thecladding material is also called clad metal. In the present example, thebusbar 2 is constituted by two layers, for example. As shown in FIGS. 3to 5 , the busbar 2 includes a metal layer 250 on the lower surface side(also referred to as lower metal layer 250) and a metal layer 260 on theupper surface side (also referred to as upper metal layer 260). Themetal layers 250 and 260 are laminated in the thickness direction of thebusbar 2. The metal layers 250 and 260 are bonded to each other by amethod such as assembly rolling, cast rolling, explosive crimping,overlay welding or diffusion welding, for example. The interface betweenthe metal layer 250 and the metal layer 260 is formed by diffusionbonding, for example.

The busbar 2 is constituted by a copper and aluminum cladding material,for example. In the present example, the lower metal layer 250 is analuminum layer, for example, and the upper metal layer 260 is a copperlayer, for example. The lower metal layer 250 is constituted by purealuminum, for example. Pure aluminum A1050 specified in JIS, forexample, is employed as this pure aluminum. The upper metal layer 260 isconstituted by oxygen-free copper, for example. Oxygen-free copper C1020specified in JIS, for example, is employed as this oxygen-free copper.

The linear expansion coefficient of the metal layer 250 is closer to thelinear expansion coefficient of the insulating member 4 than is thelinear expansion coefficient of the metal layer 260, for example. In thepresent example, the linear expansion coefficient of the insulatingmember 4 constituted by PPS is 40 ppm/° C., for example. The linearexpansion coefficient of the metal layer 250 constituted by purealuminum is 24 ppm/° C., for example. The linear expansion coefficientof the metal layer 260 constituted by oxygen-free copper is 17 ppm/° C.,for example. The linear expansion coefficient may be referred to as thethermal expansion coefficient. Also, the conductivity of the upper metallayer 260 is greater than the conductivity of the lower metal layer 250.

The upper surface and lower surface of the busbar 2 are both flat, forexample. That is, the upper surface of the upper metal layer 260 and thelower surface of the lower metal layer 250 are both flat, for example.The thickness of the metal layer 250 is set to be greater than thethickness of the metal layer 260, for example. The thickness of themetal layer 250 may, for example, be set to 3 mm, and the thickness ofthe metal layer 260 may be set to 2 mm.

The busbar 3, similarly to the busbar 2, is constituted by a claddingmaterial, for example. In the present example, the busbar 3 isconstituted by two layers, for example. As shown in FIGS. 3 to 5 , thebusbar 3 includes a metal layer 350 on the lower surface side (alsoreferred to as lower metal layer 350) and a metal layer 360 on the uppersurface side (also referred to as upper metal layer 360). The metallayers 350 and 360 are bonded to each other by a method such as assemblyrolling, cast rolling, explosive crimping, overlay welding or diffusionwelding, for example. The interface between the metal layer 350 and themetal layer 360 is formed by diffusion bonding, for example.

The busbar 3 is constituted by a copper and aluminum cladding material,for example. In the present example, the lower metal layer 350 is analuminum layer, for example, and the upper metal layer 360 is a copperlayer, for example. The lower metal layer 350 is constituted by purealuminum, for example. Pure aluminum A1050 specified in JIS, forexample, is employed as this pure aluminum. The upper metal layer 360 isconstituted by oxygen-free copper, for example. Oxygen-free copper C1020specified in JIS, for example, is employed as this oxygen-free copper.

The linear expansion coefficient of the metal layer 350 is closer to thelinear expansion coefficient of the insulating member 4 than is thelinear expansion coefficient of the metal layer 360, for example. In thepresent example, the linear expansion coefficient of the metal layer 350constituted by pure aluminum is 24 ppm/° C., for example. The linearexpansion coefficient of the metal layer 360 constituted by oxygen-freecopper is 17 ppm/° C., for example. Also, the conductivity of the uppermetal layer 360 is greater than the conductivity of the lower metallayer 350.

The lower surface of the busbar 3 is flat, for example. That is, thelower surface of the lower metal layer 350 is flat, for example. Thelower surface of the busbar 3 is located in the same plane as the lowersurface of the busbar 2, for example. On the other hand, the uppersurface of the busbar 3 has a region 301 that is one step lower than theother regions, as shown in FIG. 6 . This region 301 is a board mountingregion 301 on which the wiring board 5 is mounted. Part of the uppersurface of the main body part 30, for example, constitutes the boardmounting region 301.

In the present example, the upper surface of the upper metal layer 360is partially lower, and this lower region constitutes the board mountingregion 301. That is, the board mounting region 301 is provided on theupper surface of the upper metal layer 360. The board mounting region301 is lower than the upper surface of the busbar 2, for example. On theupper surface of the busbar 3, regions other than the board mountingregion 301 are located in the same plane as the upper surface of thebusbar 2, for example.

A plurality of conductive raised parts 302 are provided in the boardmounting region 301. The plurality of raised parts 302 are constitutedby part of the busbar 3, for example. Specifically, the plurality ofraised parts 302 are constituted by part of the metal layer 360, forexample. The raised parts 302 can be said to be molded as one piece withthe busbar 3. Also, the raised parts 302 can be said to be molded as onepiece with the metal layer 360. In the present example, the raised parts302 are part of the metal layer 360, and are thus constituted by copper,for example.

The raised parts 302 are disk-shaped, for example. When the wiring board5 is mounted in the board mounting region 301, the plurality ofprotruding units 302 are inserted into a plurality of open holes 52,described later, provided in the wiring board 5.

The plurality of raised parts 302 include four raised parts 302 arespectively corresponding to the four MOSFETs 6. Also, the plurality ofraised parts 302 includes two raised parts 302 b corresponding to theZener diode 7. The plurality of raised parts 302 a are aligned in thelong direction of the main body part 30. Of the two edge portions of themain body part 30 in the short direction thereof, the plurality ofraised parts 302 a are provided at the edge portion close to the firstportion 201 of the busbar 2. The plurality of raised parts 302 a arealigned along the first portion 201 of the busbar 2. The two raisedparts 302 b are aligned in the short direction of the main body part 30.Of the two edge portions of the main body part 30 in the long directionthereof, the two raised parts 302 b are provided at the edge portionclose to the second portion 202 of the busbar 2. Of the plurality ofraised parts 302 a, the raised part 302 a closest to the second portion202 is aligned with the two raised parts 302 b in the short direction ofthe main body part 30. The roles of the raised parts 302 a and 302 bwill be described in detail later.

The thickness of the metal layer 350 is set to be greater than thethickness of the metal layer 360, for example. The thickness of themetal layer 350 may, for example, be set to 3 mm. Also, the thickness ofthe portion of the metal layer 360 where the board mounting region 301is not provided on the upper surface may be set to 2 mm.

Example Configuration of MOSFET

FIG. 7 is a schematic plan view showing an example of the back surfaceof the MOSFET 6. Here, for convenience of description, the configurationof the MOSFET 6 will be described, with the right side and the left sidein FIG. 7 respectively being the right side and the left side of theMOSFET 6, and the up-down direction in FIG. 7 being the up-downdirection of the MOSFET 6.

The MOSFET 6 is a surface mount component, for example. As shown in FIG.7 , the MOSFET 6 includes a package 60 in which a semiconductor deviceand the like are housed. The package 60 is a leadless package, forexample. The package 60 includes a main body part 65, a gate terminal61, a plurality of source terminals 62 and a drain terminal 63. The gateterminal 61, the plurality of source terminals 62 and the drain terminal63 are provided on the back surface of the main body part 65.

The main body part 65 is constituted by a resin such as an epoxy resin,for example. The plurality of source terminals 62 are electricallyconnected to each other inside the main body part 65. The gate terminal61, the source terminals 62 and the drain terminal 63 are constituted bya metal, for example. The gate terminal 61, the source terminals 62 andthe drain terminal 63 may be constituted by oxygen-free copper, forexample. Oxygen-free copper C1020 specified in JIS, for example, isemployed as this oxygen-free copper. The gate terminal 61, the sourceterminals 62 and the drain terminal 63 may also be constituted by acopper alloy. The gate terminal 61, the source terminals 62 and thedrain terminal 63 have a flat plate shape, for example.

On the right edge portion of the back surface of the main body part 65,the gate terminal 61 and the plurality of source terminals 62 arealigned in a row in the up-down direction. The gate terminal 61 and theplurality of source terminals 62 protrude slightly outward from theright edge of the back surface of the main body part 65. The left edgeof the drain terminal 63 is uneven, and a plurality of protruding parts63 a aligned in the up-down direction are provided on the left edge. Theplurality of protruding parts 63 a protrude slightly outward from theleft edge of the back surface of the main body part 65.

Note that the shape of the package 60 is not limited to the aboveexample. The shape of the drain terminal 63 may, for example, be otherthan the shape in FIG. 7 . Also, the number of source terminals 62 thatare included in the package 60 may be other than three. The package 60may be a leaded package.

Example Configuration of Zener Diode

The configuration of the Zener diode 7 will be described with referenceto FIGS. 2 and 5 . Here, for convenience of description, theconfiguration of the Zener diode 7 will be described, with the left sideand the right side in FIG. 2 respectively being the upper side and lowerside of the Zener diode 7, and the up-down direction of FIG. 2 being theleft-right direction of the Zener diode 7.

As shown in FIGS. 2 and 5 , the Zener diode 7 includes a package 70 inwhich a semiconductor device and the like are housed. The package 70 isa leaded package, for example. The package 70 includes a main body part75, a cathode terminal 71 and anode terminals 72 and 73.

The main body part 75 is constituted by a resin such as an epoxy resin,for example. The cathode terminal 71 and the anode terminals 72 and 73are constituted by a metal, for example. The cathode terminal 71 and theanode terminals 72 and 73 may be constituted by oxygen-free copper, forexample. Oxygen-free copper C1020 specified in JIS, for example, isemployed as this oxygen-free copper. The cathode terminal 71 and theanode terminals 72 and 73 may also be constituted by a copper alloy. Thecathode terminal 71 has a flat plate shape, for example. The anodeterminals 72 and 73 are lead terminals, and have a shape in which anelongated plate-shaped portion is bent in two places, for example.

The cathode terminal 71 is provided on the back surface of the main bodypart 75. The upper edge portion of the cathode terminal 71 protrudesslightly from the upper edge of the back surface of the main body part75. The anode terminals 72 and 73 extend outward from the lower endsurface of the main body part 75 and are adjacently arranged in theleft-right direction. The distal end portions of the anode terminals 72and 73 are disposed on the wiring board 5.

Note that the shape of the package 70 is not limited to the aboveexample. The shape of at least one of the cathode terminal 71 and theanode terminals 72 and 73 may, for example, be other than the shape inFIGS. 2 and 5 . Also, the package 70 may be a leadless package.

Example Configuration of Wiring Board

FIG. 8 is a schematic perspective view showing an example of the wiringboard 5. As shown in FIGS. 6, 8 and other diagrams, the wiring board 5includes the plurality of open holes 52 that pass through in thethickness direction thereof. The plurality of open holes 52 include fouropen holes 52 a respectively corresponding to the four MOSFETs 6 and twoopen holes 52 b corresponding to the Zener diode 7, for example. Thefour open holes 52 a are provided at one edge portion of the wiringboard 5 in the short direction thereof so as to be aligned in the longdirection of the wiring board 5. The two open holes 52 b are provided atone edge portion of the wiring board 5 in the long direction thereof soas to be aligned in the short direction of the wiring board 5. Of theplurality of open holes 52 a, the open hole 52 a closest to the one endis aligned with the two open holes 52 b in the short direction of thewiring board 5. The MOSFETs 6 are respectively disposed close to theopen holes 52 a corresponding thereto. The Zener diode 7 is disposedclose to the two open holes 52 b.

The conductive layer 51 of the wiring board 5 includes a plurality ofconductive regions 53 respectively corresponding to the plurality ofMOSFETs 6, as shown in FIGS. 6, 8 and other diagrams. Also, theconductive layer 51 includes a conductive region 54 corresponding to theconnector 8 and a wiring region 55. Note that, in FIGS. 3 to 5 ,illustration of the conductive layer 51 is omitted.

The conductive regions 53 each have a land 531 to which the gateterminal 61 of the corresponding MOSFET 6 is bonded. The conductiveregions 53 each have three lands 532 to which the three source terminals62 of the corresponding MOSFET 6 are respectively bonded. Lands to whicha terminal or the like is bonded are also called pads.

Each conductive region 53 has an extension region 533 extending from theplurality of lands 532. The extension region 533 included in theconductive region 53 corresponding to each MOSFET 6 is located aroundthe open hole 52 a corresponding to the MOSFET 6. The extension region533 is provided so as to surround the opening edge of the open hole 52 a(specifically, the opening edge on the upper surface side of the wiringboard 5). The open hole 52 a can also be said to be provided in theextension region 533. The lands 532 can also be said to be protrudingparts protruding from the extension region 533.

In the present example, the open holes 52 a are through holes in which aconductive region is formed on the inner circumferential surfacethereof, for example. On the other hand, the open holes 52 b do not havea conductive region formed on the inner circumferential surface thereofand are not through holes, for example. The conductive region on theinner circumferential surface of the open holes 52 a is constituted by ametal, for example. The conductive region on the inner circumferentialsurface of the open holes 52 a may be constituted by the same materialas the conductive layer 51 or may be constituted by a differentmaterial. The conductive region on the inner circumferential surface ofeach open hole 52 a is joined to the extension region 533 around theopen hole 52 a. Note that a conductive region may not be formed on theinner circumferential surface of the open holes 52 a. Also, the openholes 52 b may be through holes in which a conductive region is formedon the inner circumferential surface thereof.

The conductive region 54 corresponding to the connector 8 includes fourlands 541 and two lands 542, for example. The two lands 542 are landsfor fixing the connector 8 to the wiring board 5. Two metal regions foruse in fixing the connector 8 are provided on the back surface of theconnector 8. The two metal regions are respectively bonded by solder tothe two lands 542, for example. A main component of the solder is tin.Also, the connector 8 includes four connection terminals 81 respectivelyelectrically connected to the gate terminals 61 of the plurality ofMOSFETs 6 (see FIG. 2 ). The connection terminals 81 are constituted bya metal, for example. The plurality of connection terminals 81 of theconnector 8 are respectively bonded to the plurality of lands 541 bysolder, for example.

The wiring region 55 includes four wirings 551 that are respectivelyelectrically connected to the gate terminals 61 of the four MOSFETs 6,for example. The plurality of wirings 551 are respectively joined at oneend to the plurality of lands 531 to which the gate terminals 61 of theplurality of MOSFETs 6 are bonded. The plurality of wirings 551 arerespectively joined at the other end to the plurality of lands 541 towhich the plurality of connection terminals 81 of the connector 8 arebonded. The gate terminals 61 are respectively electrically connected tothe connection terminals 81 of the connector 8 through the wirings 551.

The wiring board 5 having a configuration such as the above is mountedon the board mounting region 301 on the upper surface of the busbar 3.The outer shape of the board mounting region 301 has substantially thesame shape as the outer shape of the wiring board 5. FIG. 9 is a diagramshowing an example of the wiring board 5 mounted on the board mountingregion 301 of the busbar 3.

When the wiring board 5 is mounted on the board mounting region 301, theplurality of raised parts 302 a of the busbar 3 are respectivelyinserted into the plurality of open holes 52 a of the wiring board 5,and also the plurality of raised parts 302 b of the busbar 3 areinserted into the plurality of open holes 52 b of the wiring board 5. Ina state where the wiring board 5 is mounted on the board mounting region301, the raised parts 302 a protrudes from the busbar 3 into the openholes 52 a, and the raised parts 302 b protrude from the busbar 3 intothe open holes 52 b. The diameter of the raised parts 302 is setslightly smaller than the diameter of the open holes 52. The raisedparts 302 can also be said to fit into the open holes 52.

The wiring board 5 on the board mounting region 301 is located not onlyon the busbar 3 but also on the L-shaped insulation portion 42 locatedbetween the busbar 2 and the busbar 3. In the insulating portions 42,the upper end face of a surrounding portion 42 a (see FIG. 6 ) locatedaround the board mounting region 301 is flush with the upper surfaces ofthe lower metal layers 250 and 350, for example, as shown in FIGS. 4 and5 . The surrounding portion 42 a is not located between the upper metallayer 260 and the upper metal layer 360. The wiring board 5 is locatedon the board mounting region 301 and is also located above thesurrounding portion 42 a located around the board mounting region 301with a gap from the upper end face of the surrounding portion 42 a. Aninsulating member such as adhesive tape may be provided in the gap, forexample. The wiring board 5 is adjacent to the first portion 201 and thesecond portion 202 of the busbar 2. The upper surface of the insulatingboard 50 of the wiring board 5 mounted in the board mounting region 301is flush with the upper surface of the busbar 2 and with the region ofthe upper surface of the busbar 3 other than the board mounting region301. Note that the upper surface of the conductive layer 51 on theinsulating board 50 may be located in the same plane as the uppersurface of the busbar 2 and the region of the upper surface of thebusbar 3 other than the board mounting region 301.

The wiring board 5 is fixed to the board mounting region 301 by abonding material, for example. Double-sided adhesive tape, for example,is employed as the bonding material. Other members may also be employedas the bonding material. Also, the wiring board 5 may be simply placedin the board mounting region 301 and not fixed.

The upper surfaces of the raised parts 302 in the open holes 52 arelocated in the same plane as the upper surface of the conductive layer51 on the insulating board 50 of the wiring board 5, for example. Inthis case, the upper surface of the raised part 302 a in each open hole52 a will be flush with the upper surface of the extension region 533around the open hole 52 a. Note that the upper surfaces of the raisedparts 302 may be located in the same plane as the upper surface of theinsulating board 50.

Regarding Conductive Pieces

The plurality of conductive pieces 9 are respectively bonded to theplurality of raised parts 302 a exposed from the upper surface of thewiring board 5. Also, the plurality of conductive pieces 9 arerespectively bonded to the plurality of extension regions 533 of thewiring board 5. Each conductive piece 9 is provided on the wiring board5 so as to cover the upper surface of the raised part 302 a in the openhole 52 a of the wiring board 5 and a peripheral portion of the openhole 52 a. The conductive piece 9 covers the opening edge of the openhole 52 a (specifically, the opening edge on the upper surface side ofthe wiring board 5). The thickness of the conductive pieces 9 may be setfrom 0.2 mm to 0.5 mm inclusive, for example.

Each conductive piece 9 is bonded by a conductive bonding material 115to the upper surface of the raised part 302 a in the open hole 52 a andto the extension region 533 around the open hole 52 a (see FIG. 4 ).Solder, for example, is employed as the conductive bonding material 115.The conductive bonding material 115 bonds the back surface of theconductive piece 9 to the upper surface of the raised part 302 a and theextension region 533, and bonds the end faces of the conductive piece 9to the upper surface of the extension region 533. The conductive bondingmaterial 115 includes a portion located between the conductive piece 9and the raised part 302 a and extension region 533.

Note that the conductive bonding material 115 may enter the open holes52 a. In this case, the conductive region on the inner circumferentialsurface of each open hole 52 a which is a through hole and the raisedpart 302 a in the open hole 52 a may be bonded by the conductive bondingmaterial 115.

Example Implementation of Electronic Components

The MOSFETs 6 are mounted to straddle between both the busbar 2 and thewiring board 5 that is on the busbar 3. The MOSFETs 6 are, for example,mounted to straddle between the first portion 201 of the busbar 2 andthe edge portion on which the conductive regions 53 are formed in theshort direction of the wiring board 5. In other words, the MOSFETs 6 aremounted to straddle between the first portion 201 of the busbar 2 andthe portion of the wiring board 5 adjacent to the first portion 201. Asshown in FIG. 6 , the insulating portion 42 (more specifically, thesurrounding portion 42 a) is located between the first portion 201 ofthe busbar 2 and the busbar 3. The MOSFETs 6 are provided on the busbars2 and 3 so as to straddle the insulating portion 42.

The drain terminals 63 of the MOSFETs 6 are bonded by a conductivebonding material 103 (see FIGS. 2 to 4 ) to the upper surface of thefirst portion 201 of the busbar 2. Solder, for example, is employed asthe conductive bonding material 103. The conductive bonding material 103bonds the back surfaces and end faces of the drain terminals 63 to thefirst portion 201. The conductive bonding material 103 includes aportion located between the drain terminals 63 and the first portion201. The voltage that is applied to the input terminal part 21 of thebusbar 2 is applied to the drain terminals 63 bonded to the busbar 2.

The gate terminal 61 of each MOSFET 6 is bonded by a conductive bondingmaterial 101 (see FIG. 3 ) to the land 531 of the conductive region 53corresponding to the MOSFET 6. Solder, for example, is employed as theconductive bonding material 101. The conductive bonding material 101bonds the back surface and end face of the gate terminal 61 and the land531, for example. The conductive bonding material 101 includes a portionlocated between the gate terminal 61 and the land 531. The gate terminal61 is electrically connected to the connection terminal 81 of theconnector 8 through the land 531, the wiring 551 joined to the land 531,and the land 541 joined to the wiring 551. Switching control of eachMOSFET 6 is performed externally through the connector 8.

The plurality of source terminals 62 of each MOSFET 6 are respectivelybonded by a conductive bonding material 102 (see FIG. 4 ) to theplurality of lands 532 in the conductive region 53 corresponding to theMOSFET 6. Solder, for example, is employed as the conductive bondingmaterial 102. The conductive bonding material 102 bonds the backsurfaces and end faces of the source terminals 62 to the lands 532, forexample. The conductive bonding material 102 includes a portion locatedbetween the source terminals 62 and the lands 532. The source terminals62 are electrically connected to the output-side busbar 3, through thelands 532, the extension region 533 joined to the lands 532, theconductive piece 9 bonded to the extension region 533, and theconductive raised part 302 a to which the conductive piece 9 is bonded.The conductive piece 9 functions as a relay terminal that electricallyconnect the source terminals 62 and the raised part 302 a. The outputvoltage of the source terminals 62 is output externally from the outputterminal part 31 of the busbar 3.

The Zener diode 7 is mounted to straddle between both the busbar 2 andthe wiring board 5 that is on the busbar 3, similarly to the MOSFETs 6.The Zener diode 7 is, for example, mounted to straddle between thesecond portion 202 of the busbar 2 and the edge portion in which theopen holes 52 b are formed in the long direction of the wiring board 5.In other words, the Zener diode 7 is mounted to straddle between thesecond portion 202 of the busbar 2 and the portion of the wiring board 5adjacent to the second portion 202. The insulating portion 42(specifically, the surrounding portion 42 a) is located between thesecond portion 202 of the busbar 2 and the busbar 3. The Zener diode 7is provided on the busbars 2 and 3 so as to straddle the insulatingportion 42.

The cathode terminal 71 of the Zener diode 7 is bonded by a conductivebonding material 111 (see FIG. 5 ) to the upper surface of the secondportion 202 of the busbar 2. Solder, for example, is employed as theconductive bonding material 111. The conductive bonding material 111bonds the back surface and end face of the cathode terminal 71 to thesecond portion 202. The conductive bonding material 111 includes aportion located between the cathode terminal 71 and the second portion202. The cathode terminal 71 is electrically connected to the drainterminals 63 of the MOSFETs 6 through the busbar 2.

The anode terminal 72 of the Zener diode 7 is bonded to one of theraised parts 302 b in one of the open holes 52 b in the wiring board 5.The anode terminal 73 of the Zener diode 7 is bonded to the other raisedpart 302 b in the other open hole 52 b in the wiring board 5. In thepresent example, given that the raised parts 302 b are constituted bypart of the busbar 3, the anode terminals 72 and 73 can be said to bebonded to the upper surface of the busbar 3.

The anode terminal 72 is bonded by a conductive bonding material to theupper surface of one of the raised parts 302 b. Solder, for example, isemployed as the conductive bonding material. The conductive bondingmaterial electrically bonds the back surface and end face of the distalend portion of the anode terminal 72 to the one raised part 302 b. Theconductive bonding material includes a portion located between thedistal end portion of the anode terminal 72 and the one raised part 302b. The anode terminal 72 is electrically connected to the sourceterminals 62 of the MOSFETs 6 through the one raised part 302 b and thebusbar 3.

The anode terminal 73 is bonded by a conductive bonding material 112(see FIG. 5 ) to the upper surface of the other raised part 302 b.Solder, for example, is employed as the conductive bonding material 112.The conductive bonding material 112 bonds the back surface and end faceof the distal end portion of the anode terminal 73 to the other raisedpart 302 b. The conductive bonding material 112 includes a portionlocated between the distal end portion of the anode terminal 73 and theother raised part 302 b.

Example of Manufacturing Method for Circuit Structure

In the case of manufacturing the circuit structure 1A having aconfiguration such as the above, first, two pieces of a claddingmaterial 10 for producing the busbars 2 and 3 are prepared. The claddingmaterial 10 comprises metal layers 10 a and 10 b laminated one on theother, as shown in FIG. 10 . The metal layer 10 a is an aluminum layer,for example, and the metal layer 10 b is a copper layer, for example.The cladding material 10 is produced by an aluminum plate and a copperplate being diffusion bonded by rolling and heat treatment, for example.The metal layer 10 a forms the metal layer 250 of the busbar 2 or themetal layer 350 of the busbar 3. The metal layer 10 b forms the metallayer 260 of the busbar 2 or the metal layer 360 of the busbar 3.

Next, one of the two pieces of cladding material 10 that were preparedis formed into a predetermined shape by cold forging or cutting, forexample. The open hole 210 is then provided in the one piece of moldedcladding material 10. The busbar 2 is thereby completed.

Also, the other piece of cladding material 10 is formed into apredetermined shape by cold forging or cutting, for example. The openhole 310 is then provided in the other piece of shaped cladding material10. Next, the plurality of raised parts 302 are provided on the surfaceof the other piece of cladding material 10. The busbar 3 shown in FIG.11 is thereby completed.

Next, as shown in FIG. 12 , the busbars 2 and 3 are disposed in a moldfor insert molding. In FIG. 12 , illustration of the mold for insertmolding is omitted. A thermoplastic resin having excellent heatresistance such as PPS is then injected into the mold for insert moldingfrom an injection molding machine, and the busbars 2 and 3 and the resinare molded as one piece. As shown in FIG. 13 , an integrally moldedarticle in which the busbars 2 and 3 and the insulating member 4 aremolded as one piece is thereby obtained.

Next, the wiring board 5 is fixed by a bonding material such asdouble-sided adhesive tape to the board mounting region 301 of thebusbar 3 included in the produced integrally molded article. Thestructure shown in FIG. 9 mentioned above is thereby obtained.

Next, as shown in FIG. 14 , a solder paste 11 is applied topredetermined regions of the upper surfaces of the busbar 2, the busbar3 and the wiring board 5. In FIG. 14 , the solder paste 11 is shaded.The plurality of MOSFETs 6, the Zener diode 7, the connector 8 and theplurality of conductive pieces 9 are then soldered with a reflow methodto the regions to which the solder paste 11 was applied. Theabove-described circuit structure 1A shown in FIGS. 1, 2 and otherdiagrams is thereby completed.

Thereafter, as shown in FIG. 15 , a control board 910 that controls theMOSFETs 6 is attached to the circuit structure 1A. The control board 910includes a microcomputer, connectors 911 and 912 and the like, forexample. The connector 912 is connected to the connector 8 of thecircuit structure 1A. The control board 910 is electrically connected tothe gate terminals 61 of the MOSFETs 6 through the connector 912 and theconnector 8 connected thereto. The control board 910 is thereby able toperform switching control of the MOSFETs 6. A wiring member extendingfrom an external device is connected to the connector 911. The controlboard 910 performs switching control of the MOSFETs 6, in response toinstructions from the external device.

Next, as shown in FIG. 16 , a heat sink 920 is attached to the backsurfaces of the busbars 2 and 3 via a heat conductive member such as aheat dissipation sheet. Heat that is generated by the circuit structure1A is thereby dissipated externally through the heat sink 920. A case930 covering the wiring board 5, the plurality of MOSFETs 6, the Zenerdiode 7, the connector 8 and the plurality of conductive pieces 9 isthen attached to the busbars 2 and 3. The electrical junction box 900 isthereby completed.

As described above, in the present example, given that the busbar 2 isconstituted by a cladding material, the linear expansion coefficient ofthe busbar 2 as a whole can be approximated to the linear expansioncoefficient of the insulating member 4, together with bonding of thedrain terminals 63 of the MOSFETs 6 to the busbar 2 being facilitated.

Consider the case where, for example, the upper metal layer 260 isconstituted by a copper layer and the lower metal layer 250 isconstituted by an aluminum layer, as in the above example. In this case,given that the portion to which the drain terminals 63 are bonded isconstituted by copper which is easily soldered, bonding of the drainterminals 63 to the busbar 2 is facilitated. Also, given that the lowermetal layer 250 is constituted by an aluminum layer having a linearexpansion coefficient that is relatively close to the linear expansioncoefficient of the insulating member 4, the linear expansion coefficientof the busbar 2 as a whole can be approximated to the linear expansioncoefficient of the insulating member 4.

In contrast, consider the case where the busbar 2 is constituted by onlycopper (e.g., oxygen-free copper), unlike the present example. In thiscase, although the drain terminals 63 are easily soldered to the busbar2, the linear expansion coefficient of the busbar 2 (e.g., 17 ppm/° C.)will differ greatly from the linear expansion coefficient of theinsulating member 4 (e.g., 40 ppm/° C.). Given that the MOSFETs 6 areprovided on the busbars 2 and 3 so as to straddle the insulating portion42 of the insulating member 4, if the linear expansion coefficient ofthe busbar 2 differs from the linear expansion coefficient of theinsulating member 4, thermal stress could possibly occur in the bondingportion of the drain terminals 63 and the busbar 2, according to changesin ambient temperature. Cracks may thereby occur in this bondingportion, and the reliability of the bonding portion could decrease.

Also, consider the case where the busbar 2 is constituted by onlyaluminum (e.g., pure aluminum). In this case, the linear expansioncoefficient of the busbar 2 (e.g., 24 ppm/° C.) will approximate thelinear expansion coefficient of the insulating member 4, compared withthe case where the busbar 2 is constituted by only copper. Accordingly,thermal stress is less likely to occur in the bonding portion of thedrain terminals 63 and the busbar 2, as compared with the case where thebusbar 2 is constituted by only copper. However, given that it isdifficult to solder the drain terminals 63 to the busbar 2 made ofaluminum, it becomes difficult to bond the drain terminals 63 to thebusbar 2. As a result, the drain terminals 63 and the busbar 2 cannot beappropriately bonded, and the reliability of the bonding portion of thedrain terminals 63 and the busbar 2 could decrease.

In the present example, given that the busbar 2 is constituted by acladding material, a material that bonds easily can be used as thematerial of the portion of the busbar 2 to which the drain terminals 63of the MOSFETs 6 are bonded, as in the above example. Thus, the drainterminals 63 can be easily bonded to the busbar 2. On the other hand,the linear expansion coefficient of a material that bonds easily maydiffer greatly from the linear expansion coefficient of the insulatingmember 4. Even in this case, by selecting a material whose linearexpansion coefficient is close to the linear expansion coefficient ofthe insulating member 4 as the material of other portions constitutingthe busbar 2, the linear expansion coefficient of the busbar 2 as awhole can be approximated to the linear expansion coefficient of theinsulating member 4. Thermal stress is thereby less likely to occur inthe bonding portion of the drain terminals 63 and the busbar 2, togetherwith bonding of the drain terminals 63 to the busbar 2 beingfacilitated. As a result, the reliability of the bonding portionimproves. Also, since heat generated by the MOSFETs 6 can be transferreddirectly to the busbar 2, local increases in temperature are less likelyto occur. Similarly, thermal stress is less likely to occur in thebonding portion of the cathode terminal 71 and the busbar 2, togetherwith bonding of the cathode terminal 71 to the busbar 2 beingfacilitated. As a result, the reliability of the bonding portionimproves.

In the present example, given that the busbar 3 is constituted by acladding material, the linear expansion coefficient of the entire busbar3 can be approximated to the linear expansion coefficient of theinsulating member 4, together with bonding of the anode terminals 72 and73 of the Zener diode 7 to the busbar 3 (specifically, the raised parts302 b) being facilitated. Thermal stress is thereby less likely to occurin the bonding portion of the anode terminals 72 and 73 and the busbar3, together with bonding of the anode terminals 72 and 73 to the busbar3 being facilitated. As a result, the reliability of the bonding portionimproves.

In the present example, given that the busbar 2 includes the metal layer250 and the metal layer 260 laminated thereon, the busbar 2 made of acladding material can be easily produced by laminating the metal layers250 and 260. Also, in the case where the metal layer that is used as themetal layer 260 bonds more easily to the drain terminals 63 and thecathode terminal 71 than does the metal layer 250, the linear expansioncoefficient of the busbar 2 as a whole can be approximated to the linearexpansion coefficient of the insulating member 4, while at the same timefacilitating bonding of the drain terminals 63 and the cathode terminal71 to the metal layer 260. Similarly, the busbar 3 made of a claddingmaterial can be easily produced by laminating the metal layers 350 and360. Also, in the case where the metal layer that is used as the metallayer 360 bonds more easily to the anode terminals 72 and 73 than doesthe metal layer 350, the linear expansion coefficient of the busbar 3 asa whole can be approximated to the linear expansion coefficient of theinsulating member 4, while at the same time facilitating bonding of theanode terminals 72 and 73 to the metal layer 360.

Also, with the busbar 2 according to the present example, given that themetal layer 250 is an aluminum layer and the metal layer 260 is a copperlayer, the busbar 2 made of a cladding material can be easily producedusing aluminum and copper. Also, copper bonds more easily to the drainterminals 63 and the cathode terminal 71 than aluminum, whereas aluminumhas a linear expansion coefficient closer to the insulating member 4than copper. Accordingly, the linear expansion coefficient of the busbar2 as a whole can be approximated to the linear expansion coefficient ofthe insulating member 4, while at the same time facilitating bonding ofthe drain terminals 63 and the cathode terminal 71 to the metal layer260. Similarly, the busbar 3 made of a cladding material can be easilyproduced using aluminum and copper. Also, copper bonds more easily tothe anode terminals 72 and 73 than aluminum, whereas aluminum has alinear expansion coefficient closer to the insulating member 4 thancopper. Accordingly, the linear expansion coefficient of the busbar 3 asa whole can be approximated to the linear expansion coefficient of theinsulating member 4, while at the same time facilitating bonding of theanode terminals 72 and 73 to the metal layer 360.

Also, in the present example, given that the linear expansioncoefficient of the metal layer 250 is closer to the linear expansioncoefficient of the insulating member 4 than is the linear expansioncoefficient of the metal layer 260, a metal layer having a linearexpansion coefficient close to the linear expansion coefficient of theinsulating member 4 can be employed as the metal layer 250, withoutconsidering bondability to the drain terminals 63 and the cathodeterminal 71. Similarly, given that the linear expansion coefficient ofthe metal layer 350 is closer to the linear expansion coefficient of theinsulating member 4 than is the linear expansion coefficient of themetal layer 360, a metal layer having a linear expansion coefficientclose to the linear expansion coefficient of the insulating member 4 canbe employed as the metal layer 350, without considering bondability tothe anode terminals 72 and 73.

Also, in the present example, the upper end face of the insulatingportion 42 of the insulating member 4 is flush with the upper surface ofthe lower metal layer 250 having a linear expansion coefficient close tothe linear expansion coefficient of the insulating member 4 (e.g., seeFIG. 4 ). The upper metal layer 260 is thereby less likely to beaffected by deformation of the insulating portion 42 caused by changesin ambient temperature. As a result, thermal stress is less likely tooccur in the bonding portion of the upper metal layer 260 and the drainterminals 63 and cathode terminal 71. Accordingly, a metal layer havinga large difference in linear expansion coefficient from the insulatingmember 4 can be used as the metal layer 260.

Also, in the present example, the upper end face of the insulatingportion 42 is flush with the upper surface of the lower metal layer 350having a linear expansion coefficient close to the linear expansioncoefficient of the insulating member 4 (e.g., see FIG. 5 ). The uppermetal layer 360 is thereby less likely to be affected by deformation ofthe insulating portion 42 caused by changes in ambient temperature. As aresult, thermal stress is less likely to occur in the bonding portion ofthe upper metal layer 360 and the anode terminals 72 and 73.Accordingly, a metal layer having a large difference in linear expansioncoefficient from the insulating member 4 can be used as the metal layer360.

Also, in the present example, the upper end face of the insulatingportion 42 is flush with the upper surface of the lower metal layer 250and the lower metal layer 350, and the lower metal layer 250 and thelower metal layer 350 are constituted by the same type of metal, such asaluminum, for example. The distribution of thermal stress in a directionalong the upper surfaces of both the lower metal layer 250 and the lowermetal layer 350 thus occurs symmetrically across the insulating member 4(left-right direction in FIG. 3 to FIG. 5 ), and the thermal stressesthat occur on both sides cancel each other out. As a result, thermalstress is less likely to occur in the bonding portions of the uppermetal layer 260 and the drain terminals 63 and cathode terminal 71(e.g., see FIGS. 3 and 5 ), and the reliability of the bonding portionsimproves. Similarly, thermal stress is less likely to occur in thebonding portions (e.g., see FIGS. 3 and 4 ) of the wiring board 5 on theupper metal layer 360 and the gate terminals 61 and source terminals 62,and the reliability of the bonding portions improves. Similarly, thermalstress is less likely to occur in the bonding portions of the uppermetal layer 360 and the anode terminals 72 and 73 (e.g., see FIG. 5 ),and the reliability of the bonding portions improves.

Also, by increasing the thickness of the lower metal layer 250 having alinear expansion coefficient close to the linear expansion coefficientof the insulating member 4 to greater than the thickness of the uppermetal layer 260, as in the present example, the linear expansioncoefficient of the busbar 2 as a whole can be further approximated tothe linear expansion coefficient of the insulating member 4. As aresult, thermal stress is less likely to occur in the bonding portion ofthe drain terminals 63 and the busbar 2, and the reliability of thebonding portion further improves. Similarly, by increasing the thicknessof the lower metal layer 350 to greater than the thickness of the uppermetal layer 360, the linear expansion coefficient of the entire busbar 3can be further approximated to the linear expansion coefficient of theinsulating member 4. As a result, the reliability of the bonding portionof the anode terminals 72 and 73 and the busbar 3 further improves.

Also, in the present example, given that the busbar 2, the busbar 3 andthe insulating member 4 are molded as one piece, a member forintegrating the busbar 2, the busbar 3 and the insulating member 4 isnot required. The configuration of the circuit structure 1A can therebybe simplified.

Also, in the present example, the conductive raised parts 302 a protrudefrom the busbar 3 into the open holes 52 a in the wiring board 5. Byelectrically connecting the source terminals 62 on the wiring board 5 tothe raised parts 302 a in the open holes 52 a, the source terminals 62can thus be easily electrically connected to the busbar 3.

Also, in the present example, the conductive raised parts 302 b protrudefrom the busbar 3 into the open holes 52 b in the wiring board 5. Byelectrically connecting the anode terminals 72 and 73 on the wiringboard 5 to the raised parts 302 b in the open holes 52 b, the anodeterminals 72 and 73 can thus be easily electrically connected to thebusbar 3.

In the present example, given that the raised parts 302 are constitutedby part of the busbar 3, electrical resistance between the sourceterminals 62 and the busbar 3 can be reduced, and also electricalresistance between the anode terminals 72 and 73 and the busbar 3 can bereduced.

Also, in the present example, given that the anode terminals 72 and 73are bonded to the raised parts 302 b, as shown in FIGS. 2, 5 and otherdiagrams, electrical resistance between the anode terminals 72 and 73and the busbar 3 can be reduced.

Also, in the present example, the conductive pieces 9 bonded to theextension regions 533 that extend from the lands 532 to which the sourceterminals 62 are bonded and are located around the open holes 52 a andto the upper surfaces of the raised parts 302 a in the open holes 52 aare provided. Due to these conductive pieces 9, electrical resistancebetween the source terminals 62 and the busbar 3 can be reduced. Also,given that transfer of heat generated by the MOSFETs 6 to the busbar 3is facilitated by the conductive pieces 9, local increases intemperature are less likely to occur.

Also, in the present example, the extension regions 533 surround theopen holes 52 a, and the conductive pieces 9 cover the opening edges ofthe open holes 52 a. The bonding area of the conductive pieces 9 and theextension regions 533 and raised parts 302 a can thereby be increased.As a result, electrical resistance between the source terminals 62 andthe busbar 3 can be further reduced.

Also, in the present example, given that the wiring board 5 is locatedon the board mounting region 301, which is lower than the upper surfaceof the busbar 2, on the upper surface of the busbar 3, a difference inlevel between the wiring board 5 and the busbar 2 can be suppressed.Therefore, the MOSFETs 6 and the Zener diode 7 can be easily provided tostraddle between the wiring board 5 and the busbar 2.

Also, in the present example, given that the gate terminals 61 andsource terminals 62 of the MOSFETs 6 are insulated on the wiring board5, the gate terminals 61 and the source terminals 62 can beappropriately insulated, even if the spacing of the gate terminals 61and the source terminals 62 decreases. Therefore, a package having anarrow pitch in which the terminal spacing is narrow can be employed asthe package 60.

Note that the linear expansion coefficient of the wiring board 5 may becloser to the linear expansion coefficient of the insulating member 4(e.g., 40 ppm/° C.) than are the linear expansion coefficients of theupper metal layers 260 and 360 (e.g., 17 ppm/° C.). The linear expansioncoefficient of the wiring board 5 may, for example, be 18 ppm/° C. orgreater. The linear expansion coefficient of the wiring board 5 may becloser to the linear expansion coefficient of the insulating member 4(e.g., 40 ppm/° C.) than are the linear expansion coefficients of thelower metal layers 250 and 350 (e.g., 24 ppm/° C.). The linear expansioncoefficient of the wiring board 5 may, for example, be 25 ppm/° C. orgreater. Thermal stress is thereby less likely to occur in the bondingportion of the wiring board 5 and the gate terminals 61 and sourceterminals 62. As a result, the reliability of the bonding portionimproves.

Also, in the case of connecting the connection terminal of the wiringmember extending from the battery to the input terminal part 21 of thebusbar 2, the connection terminal of the wiring member may be brought incontact with the upper metal layer 260. The conductivity of the uppermetal layer 260 is greater than the conductivity of the lower metallayer 250. By bringing the connection terminal of the wiring member incontact with the upper metal layer 260, electrical resistance betweenthe input terminal part 21 and the battery can be reduced.

Also, in the case of connecting the connection terminal of the wiringmember extending from an electrical component to the output terminalpart 31 of the busbar 3, the connection terminal of the wiring membermay be brought in contact with the upper metal layer 360. Theconductivity of the upper metal layer 360 is greater than theconductivity of the lower metal layer 350. By bringing the connectionterminal of the wiring member in contact with the upper metal layer 360,electrical resistance between the output terminal part 31 and theelectrical component can be reduced.

Embodiment 2

FIG. 17 is a schematic perspective view showing an example of a circuitstructure 1B according to the present embodiment. FIG. 18 is a schematicplan view showing an example of the circuit structure 1B. FIG. 19 is aschematic view showing an example of the cross-sectional structure takenalong a line indicated by arrows D-D in FIG. 18 . FIG. 20 is a schematicview showing an example of the cross-sectional structure taken along aline indicated by arrows E-E in FIG. 18 . FIG. 21 is a schematic viewshowing an example of the cross-sectional structure taken along a lineindicated by arrows F-F in FIG. 18 . FIG. 22 is a schematic perspectiveview showing an example of an input-side busbar 12, an output-sidebusbar 13 and a relay busbar 16 that are included in the circuitstructure 1B. Hereinafter, the structure of the circuit structure 1Bwill be described focusing on the differences from the circuit structure1A described above.

Outline of Circuit Structure

The circuit structure 1B includes the input-side busbar 12 (also simplyreferred to as busbar 12), the output-side busbar 13 (also simplyreferred to as busbar 13), the relay busbar 16 (also simply referred toas busbar 16) and a wiring board 15. The busbars 12, 13 and 16 areconductive members. The circuit structure 1B further includes theabove-described MOSFET 6, Zener diode 7, connector 8 and conductivepiece 9. In the present example, the circuit structure 1B includes eightMOSFETs 6, two Zener diodes 7, two connectors 8 and four conductivepieces 9, for example. Note that the numbers of MOSFETs 6, Zener diodes7, connectors 8 and conductive pieces 9 included in the circuitstructure 1B are not limited thereto.

The drain terminals 63 of four of the eight MOSFETs 6 and the cathodeterminal 71 of one of the two Zener diodes 7 are electrically connectedto the input-side busbar 12. The drain terminals 63 of the four MOSFETs6 and the cathode terminal 71 of the one Zener diode 7 are therebyelectrically connected to each other.

The drain terminals 63 of the remaining four of the eight MOSFETs 6 andthe cathode terminal 71 of the other of the two Zener diodes 7 areelectrically connected to the output-side busbar 13. The drain terminals63 of the remaining four MOSFETs 6 and the cathode terminal 71 of theother Zener diode 7 are thereby electrically connected to each other.

The source terminals 62 of the eight MOSFETs 6 and the anode terminals72 and 73 of the two Zener diodes 7 are electrically connected to therelay busbar 16. The source terminals 62 of the eight MOSFETs 6 and theanode terminals 72 and 73 of the two Zener diodes 7 are therebyelectrically connected to each other.

Hereafter, the MOSFETs 6 whose drain terminal 63 is electricallyconnected to the busbar 12 may be referred to as MOSFETs 6 a. Also, theMOSFETs 6 whose drain terminal 63 is electrically connected to thebusbar 13 may be referred to as MOSFETs 6 b. Also, the Zener diode 7whose cathode terminal 71 is electrically connected to the busbar 12 maybe referred to as Zener diode 7 a. Also, the Zener diode 7 whose cathodeterminal 71 is electrically connected to the busbar 13 may be referredto as Zener diode 7 b.

The input-side busbar 12 is modified in shape from the busbar 2 of thecircuit structure 1A described above. The busbar 12 is a plate-shapedmetal member elongated in one direction, for example. The upper surfaceand lower surface of the busbar 12 are flat, for example. The busbar 12includes a main body part 120 and an input terminal part 121, forexample. The main body part 120 is a rectangular plate-shaped portion,for example. The drain terminals 63 of the MOSFETs 6 a and the cathodeterminal 71 of the Zener diode 7 a are electrically connected to themain body part 120. The input terminal part 121 protrudes from one edgeof the main body part 120 in the long direction thereof. The inputterminal part 121 has an open hole 1210 that passes through in thethickness direction thereof. A wiring member extending from the batteryis connected to the input terminal part 121 by utilizing the open hole1210, for example. The output voltage of the battery is applied to theinput terminal part 121 through the wiring member. The output voltage ofthe battery applied to the input terminal part 121 is applied to thedrain terminals of the MOSFETs 6 a through the main body part 120.

The output-side busbar 13 is modified in shape from the busbar 3 of thecircuit structure 1A. The busbar 13 is a plate-shaped metal memberelongated in one direction, similarly to the busbar 12. The busbar 13has the shape of the busbar 12 inverted with the long direction thereofas the axis of symmetry. The busbar 13 includes a main body part 130 andan output terminal part 131, for example. The main body part 130 is arectangular plate-shaped portion, for example. The main body part 130 iselectrically connected to the drain terminals 63 of the MOSFETs 6 b andthe cathode terminal 71 of the Zener diode 7 b. The output terminal part131 protrudes from one edge of the main body part 130 in the longdirection thereof. The output terminal part 131 has an open hole 1310that passes through in the thickness direction thereof. A wiring memberextending from an electrical component is connected to the outputterminal part 131 by utilizing the open hole 1310, for example. Thevoltage that is output by the drain terminals of the MOSFETs 6 b isapplied to the output terminal part 131. The voltage applied to theoutput terminal part 131 is applied as a power supply to the electricalcomponent through the wiring member, for example.

As shown in FIG. 22 , the relay busbar 16 is a rectangular plate-shapedmetal member, for example. The busbars 12, 13 and 16 are located in thesame plane, for example. The busbars 12 and 13 are disposed opposingeach other with a gap therebetween such that the long directions thereofare parallel to each other. The busbar 16 is located between the busbars12 and 13 such that the long direction thereof is parallel to the longdirections of the busbars 12 and 13. The busbar 16 is located betweenthe main body part 120 of the busbar 12 and the main body part 130 ofthe busbar 13. The busbar 16 is electrically connected to the sourceterminals 62 of the eight MOSFETs 6 and the anode terminals 72 and 73 ofthe two Zener diodes 7.

An insulating member 14 is modified in shape from the insulating member4 of the circuit structure 1A. The insulating member 14 holds thebusbars 12, 13 and 16, while at the same time electrically insulatingthe busbars 12, 13 and 16 from each other. The insulating member 14 ismolded as one piece with the busbars 12, 13 and 16, for example. Theinsulating member 14 is molded as one piece with the busbars 12, 13 and16 by insert molding, for example.

FIG. 23 is a schematic perspective view showing an example of anintegrally molded article in which the busbars 12, 13 and 16 and theinsulating member 14 are molded as one piece and the wiring board 15. InFIG. 23 , the wiring board 15 to be mounted on the busbar 16 is shownseparated from the busbar 16.

As shown in FIGS. 17, 23 and other diagrams, the insulating member 14includes a frame-shaped insulating portion 141, for example. Theframe-shaped insulating portion 141 surrounds the main body part 120,the main body part 130 and the busbar 16 therebetween. The insulatingmember 14 includes an insulating portion 142 located between the busbars12 and 16 and an insulating portion 143 located between the busbars 13and 16, in addition to the insulating portion 141. The busbars 12 and 16are electrically insulated by the insulating portion 142. The busbars 13and 16 are electrically insulated by the insulating portion 143.

The wiring board 15 is modified in shape from the wiring board 5 of thecircuit structure 1A. The wiring board 15 is provided on the busbar 16.The wiring board 15 includes an insulating board 50 and a conductivelayer 51 provided on the insulating board 50, for example, similarly tothe wiring board 5.

Two connectors 8 are provided on the wiring board 5. The two connectors8 include a connector 8 a to which the gate terminals 61 of theplurality of MOSFETs 6 a are electrically connected through theconductive layer 51 of the wiring board 5, and a connector 8 b to whichthe gate terminals 61 of the plurality of MOSFETs 6 b are electricallyconnected through the conductive layer 51. Switching control of theMOSFETs 6 a is performed externally through the connector 8 a. Switchingcontrol of the MOSFETs 6 b is performed externally through the connector8 b.

In the present example, one MOSFETs 6 a and one MOSFETs 6 b are disposedso as to oppose each other. The MOSFETs 6 a and MOSFETs 6 b disposedopposing each other constitute FET pairs. The circuit structure 1Bincludes four FET pairs. The four conductive pieces 9 are respectivelyprovided in correspondence with the four FET pairs. The conductivepieces 9 are each provided in order to reduce electrical resistancebetween the source terminals 62 of the MOSFETs 6 a and 6 b constitutingthe FET pair corresponding thereto and the busbar 16.

Detailed Description of Circuit Structure Example Configuration ofBusbar

The busbars 12 and 13 are both constituted by a cladding material, forexample. The busbar 12 includes a lower metal layer 250 and an uppermetal layer 260, similarly to the busbar 2. The busbar 13 includes alower metal layer 350 and an upper metal layer 360, similarly to thebusbar 3. In the present example, the thickness of the metal layer 250is similarly set to be greater than the thickness of the metal layer260, for example. The thickness of the metal layer 250 may, for example,be set to 3 mm, and the thickness of the metal layer 260 may, forexample, be set to 2 mm. Also, the thickness of the metal layer 350 issimilarly set to be greater than the thickness of the metal layer 360,for example. The thickness of the metal layer 350 may, for example, beset to 3 mm, and the thickness of the metal layer 360 may, for example,be set to 2 mm.

The busbar 16 is constituted by a cladding material, for example,similarly to the busbars 12 and 13. In the present example, the busbar16 is constituted by two layers, for example. As shown in FIGS. 19 to 22, the busbar 16 includes a metal layer 650 on the lower surface side(also referred to as lower metal layer 650) and a metal layer 660 on theupper surface side (also referred to as upper metal layer 660). Themetal layers 650 and 660 are bonded to each other by a method such asassembly rolling, cast rolling, explosive crimping, overlay welding ordiffusion welding, for example. The interface between the metal layer650 and the metal layer 660 is formed by diffusion bonding, for example.

The busbar 16 is constituted by a copper and aluminum cladding material,for example. In the present example, the lower metal layer 650 is analuminum layer, for example, and the upper metal layer 660 is a copperlayer, for example. The lower metal layer 650 is constituted by purealuminum, for example. Pure aluminum A1050 specified in JIS, forexample, is employed as this pure aluminum. The upper metal layer 660 isconstituted by oxygen-free copper, for example. Oxygen-free copper C1020specified in JIS, for example, is employed as this oxygen-free copper.

The linear expansion coefficient of the metal layer 650 is closer to thelinear expansion coefficient of the insulating member 14 than is thelinear expansion coefficient of the metal layer 660, for example. In thepresent example, the linear expansion coefficient of the metal layer 650constituted by pure aluminum is 24 ppm/° C., for example. The linearexpansion coefficient of the metal layer 660 constituted by oxygen-freecopper is 17 ppm/° C., for example.

The upper surface of the busbar 16 is, throughout its entirety, slightlylower than the upper surface of the busbars 12 and 13. The upper surfaceof the busbar 16 is lower than the upper surface of the busbars 12 and13 by the thickness of the wiring board 15, for example. The outer shapeof the upper surface of the busbar 16 is substantially the same as theouter shape of the wiring board 15.

A plurality of conductive raised parts 160 are provided on the uppersurface of the busbar 16. The plurality of raised parts 160 areconstituted by part of the busbar 16, for example. Specifically, theplurality of raised parts 160 are constituted by part of the upper metallayer 660, for example. In the present example, the raised parts 160 arepart of the upper metal layer 660, and are thus constituted by copper,for example.

The plurality of raised parts 160 are aligned in a row in the longdirection of the busbar 16. The raised parts 160 are disc-shaped, forexample. When the wiring board 15 is placed on the busbar 16, theplurality of raised parts 160 are respectively inserted into a pluralityof open holes 152, described later, provided in the wiring board 15.

The plurality of raised parts 160 include four raised parts 160 crespectively corresponding to the four FET pairs. The plurality ofraised parts 160 include two raised parts 160 a corresponding to theZener diode 7 a. The plurality of raised parts 160 include two raisedparts 160 b corresponding to the Zener diode 7 b. The two raised parts160 a are provided at one end of a row formed by the plurality of raisedparts 160, the two raised parts 160 b are provided at the other end ofthe row, and the four raised parts 160 c are located between the tworaised parts 160 a and the two raised parts 160 b.

The thickness of the metal layer 650 is set to be greater than thethickness of the metal layer 660, for example. The thickness of themetal layer 650 may, for example, be set to 3 mm, and the thickness ofthe portion of the metal layer 660 where the raised parts 160 arepresent may, for example, be set to 2 mm. The conductivity of the metallayer 660 is greater than the conductivity of the metal layer 650.

Example Configuration of Wiring Board

As shown in FIG. 23 and other diagrams, the wiring board 15 includes theplurality of open holes 152 that pass through in the thickness directionthereof. The plurality of open holes 152 are aligned in a row in thelong direction of the wiring board 15. The plurality of open holes 152includes a plurality of open holes 152 c respectively corresponding tothe four FET pairs. Also, the plurality of open holes 152 includes twoopen holes 152 a corresponding to the Zener diode 7 a and two open holes152 b corresponding to the Zener diode 7 b. The two open holes 152 a arelocated at one end of a row constituted by the plurality of open holes152, and the two open holes 152 b are located at the other end of therow. The four open holes 152 c are located between the two open holes152 a and the two open holes 152 b.

The FET pairs are disposed close to the open holes 152 c correspondingthereto. The Zener diode 7 a is disposed close to the two open holes 152a. The Zener diode 7 b is disposed close to the two open holes 152 b.

The conductive layer 51 of the wiring board 15 includes four conductiveregions 155 respectively corresponding to the four FET pairs. Also, theconductive layer 51 of the wiring board 15 includes two of theabove-described conductive regions 54 respectively corresponding to theconnectors 8 a and 8 b. Hereafter, the conductive region 54corresponding to the connector 8 a may be referred to as conductiveregion 54 a, and the conductive region 54 corresponding to the connector8 b may be referred to as conductive region 54 b. Note that, in FIGS. 19to 21 , illustration of the conductive layer 51 is omitted.

The conductive regions 155 have lands 156 a and 156 b to which the gateterminals 61 of the MOSFETs 6 a and 6 b constituting the FET pairscorresponding thereto are respectively bonded. Also, the conductiveregions 155 include a plurality of lands 157 a to which the plurality ofsource terminals 62 of the MOSFETs 6 a in the FET pairs correspondingthereto are respectively bonded. Also, the conductive regions 155include a plurality of lands 157 b to which the plurality of sourceterminals 62 of the MOSFETs 6 b in the FET pairs corresponding theretoare respectively bonded. Also, the conductive regions 155 include anextension region 158 extending from the plurality of lands 157 a and theplurality of lands 157 b. The plurality of lands 157 a and the pluralityof lands 157 b can also be said to be connected by the extension region158.

The extension region 158 included in the conductive region 155corresponding to each FET pair is located around the open hole 152 ccorresponding to the FET pair. The extension region 158 is provided soas to surround the open hole 152 c. The open hole 152 c can also be saidto be provided in the extension region 158. The lands 157 a and 157 bcan also be said to be protruding parts protruding from the extensionregion 158.

In the present example, the open holes 152 c are through holes in whicha conductive region is formed on the inner circumferential surfacethereof, for example. On the other hand, the open holes 152 a and 152 bdo not have a conductive region formed on the inner circumferentialsurface thereof and are not through holes, for example. The conductiveregion on the inner circumferential surface of the open holes 152 c isconstituted by a metal, for example. The conductive region on the innercircumferential surface of the open holes 152 c may be constituted bythe same material as the conductive layer 51 or may be constituted by adifferent material. The conductive region on the inner circumferentialsurface of each open hole 152 c is joined to the extension region 158around the open hole 152 c. Note that a conductive region may not beformed on the inner circumferential surface of the open holes 152 c.Also, the open holes 152 a and 152 b may be through holes in which aconductive region is formed on the inner circumferential surfacethereof.

The conductive regions 54 a and 54 b are located on the outer side ofthe plurality of open holes 152. The conductive regions 54 a and 54 bare respectively located at either edge portion of the wiring board 15in the long direction thereof. The two lands 542 included in theconductive region 54 a are respectively bonded by solder, for example,to two metal regions for use in fixing the connector 8 a that areprovided on the back surface of the connector 8 a. The four lands 541included in the conductive region 54 a are respectively bonded bysolder, for example, to the four connection terminals 81 included in theconnector 8 a. The two lands 542 included in the conductive region 54 bare respectively bonded by solder, for example, to two metal regions foruse in fixing the connector 8 a that are provided on the back surface ofthe connector 8 b. The four lands 541 included in the conductive region54 b are respectively bonded by solder, for example, to the fourconnection terminals 81 included in the connector 8 b.

The conductive layer 51 of the wiring board 15 also includes a wiringregion. The wiring region includes a plurality of first wiringsrespectively electrically connected to the gate terminals 61 of theplurality of MOSFETs 6 a. The plurality of first wirings arerespectively joined at one end to the plurality of lands 156 a to whichthe gate terminals 61 of the plurality of MOSFETs 6 a are bonded. Theplurality of first wirings are respectively joined at the other end tothe plurality of lands 541 to which the plurality of connectionterminals 81 of the connector 8 a are bonded. The gate terminals 61 ofthe MOSFETs 6 a are electrically connected to the connection terminals81 of the connector 8 a through the first wirings. Also, the wiringregion includes a plurality of second wirings respectively electricallyconnected to the gate terminals 61 of the plurality of MOSFETs 6 b. Theplurality of second wires are respectively joined at one end to theplurality of lands 156 b. The plurality of second wirings are joined atthe other end to the plurality of lands 541 to which the plurality ofconnection terminals 81 of the connector 8 b are bonded. The gateterminals 61 of the MOSFETs 6 b are electrically connected to theconnection terminals 81 of the connector 8 b through the second wirings.

The wiring board 15 having a configuration such as the above is mountedon the upper surface of the busbar 16. FIG. 24 is a diagram showing anexample in which the wiring board 15 is mounted on the busbar 16.

When the wiring board 15 is mounted on the busbar 16, the plurality ofraised parts 160 c are respectively inserted into the plurality of openholes 152 c, the plurality of raised parts 160 a are respectivelyinserted into the plurality of open holes 152 a, and the plurality ofraised parts 160 b are respectively inserted into the plurality of openholes 152 b. The diameter of the raised parts 160 is set slightlysmaller than the diameter of the open holes 152.

The wiring board 15 is located not only on the busbar 16 but also on theinsulating portion 142 located between the busbars 12 and 16 and on theinsulating portion 143 located between the busbars 13 and 16. The wiringboard 15 is adjacent to the main body part 120 of the busbar 12 and themain body part 130 of the busbar 13. The upper end faces of theinsulating portions 142 and 143 are flush with the upper surface of thelower metal layers 250, 350 and 650, for example, as shown in FIGS. 19to 21 . The upper surface of the insulating board 50 of the wiring board15 on the busbar 16 is flush with the upper surface of the busbars 12and 13. Note that the upper surface of the conductive layer 51 on theinsulating board 50 may be located in the same plane as the uppersurfaces of the busbars 12 and 13.

The wiring board 15 is fixed to the busbar 16 by a bonding material, forexample. Double-sided adhesive tape, for example, is employed as thebonding material. Other members may also be employed as the bondingmaterial. Also, the wiring board 15 may be simply placed on the busbar16 and not fixed.

The upper surfaces of the raised parts 160 in the open holes 152 arelocated in the same plane as the upper surface of the conductive layer51 on the insulating board 50 of the wiring board 15, for example. Inthis case, the upper surface of the raised part 160 c in each open hole152 c will be flush with the upper surface of the extension region 158around the open hole 152 c. Note that the upper surfaces of the raisedparts 160 may be located in the same plane as the upper surface of theinsulating board 50 of the wiring board 15.

Regarding Conductive Pieces

The plurality of conductive pieces 9 are respectively bonded to theplurality of raised parts 160 c exposed from the upper surface of thewiring board 15. Also, the plurality of conductive pieces 9 arerespectively bonded to the plurality of extension regions 158 of thewiring board 15. Each conductive piece 9 is provided on the wiring board15 so as to cover the upper surface of the raised part 160 c in the openhole 152 c in the wiring board 15 and a peripheral portion of the openhole 152 c. The conductive piece 9 covers the opening edge of the openhole 152 c (specifically, the opening edge on the upper surface side ofthe wiring board 15). Each conductive piece 9 is bonded by theabove-described conductive bonding material 115 to the upper surface ofthe raised part 160 c in the open hole 152 c and the extension region158 around the open hole 152 c (see FIG. 20 ). The conductive bondingmaterial 115 includes a portion located between the conductive piece 9and the raised part 160 c and extension region 158.

Note that the conductive bonding material 115 may enter the open holes152 c. In this case, the conductive region on the inner circumferentialsurface of each open hole 152 c which is a through hole and the raisedpart 160 c in the open hole 152 c may be bonded by the conductivebonding material 115.

Example Implementation of Electronic Components

The MOSFETs 6 a are mounted to straddle between both the busbar 12 andthe wiring board 15 that is on the busbar 16. As shown in FIGS. 19 and20 , the insulating portion 142 is located between the busbar 12 and thebusbar 16. The MOSFETs 6 a are provided on the busbars 12 and 16 so asto straddle the insulating portion 142.

The MOSFETs 6 b are mounted to straddle between both the busbar 13 andthe wiring board 15 that is on the busbar 16. As shown in FIGS. 19 and20 , the insulating portion 143 is located between the busbar 13 and thebusbar 16. The MOSFETs 6 b are provided on the busbars 13 and 16 so asto straddle the insulating portion 143.

The drain terminals 63 of the MOSFETs 6 a are bonded by the conductivebonding material 103 to the upper surface of the busbar 12, similarly toas described above. The voltage applied to the input terminal part 121of the busbar 12 is applied to the drain terminals 63 of the MOSFETs 6 abonded to the busbar 12.

The drain terminals 63 of the MOSFETs 6 b are bonded to the uppersurface of the busbar 13 by the conductive bonding material 103,similarly to as described above. The output voltage of the drainterminals 63 of the MOSFETs 6 b is output externally from the outputterminal part 131 of the busbar 13.

The gate terminals 61 of the MOSFETs 6 a and 6 b constituting each FETpair are respectively bonded by the conductive bonding material 101,similarly to as described above, to the lands 156 a and 156 b includedin the conductive region 155 corresponding to the FET pair. The gateterminal 61 of the MOSFET 6 a is electrically connected to theconnection terminal 81 of the connector 8 a through the land 156 a, thewiring region included in the conductive layer 51 and the land 541. Thegate terminal 61 of the MOSFET 6 b is electrically connected to theconnection terminal 81 of the connector 8 b through the land 156 b, thewiring region included in the conductive layer 51 and the land 541.Switching control of each MOSFET 6 a is performed externally through theconnector 8 a. Switching control of each MOSFET 6 b is performedexternally through the connector 8 b.

The plurality of source terminals 62 of the MOSFET 6 a of each FET pairare respectively bonded by the conductive bonding material 102,similarly to as described above, to the plurality of lands 157 aincluded in the conductive region 155 corresponding to the FET pair. Theplurality of source terminals 62 of the MOSFET 6 b of each FET pair arerespectively bonded by the conductive bonding material 102 to theplurality of lands 157 b included in the conductive region 155corresponding to the FET pair. The source terminals 62 of the MOSFET 6 aare electrically connected to the output-side busbar 13 through thelands 157 a, the extension region 158 joined to the lands 157 a, theconductive piece 9 bonded to the extension region 158, and theconductive raised part 160 c to which the conductive piece 9 is bonded.Also, the source terminals 62 of the MOSFET 6 b are electricallyconnected to the output-side busbar 13 through the lands 157 b, theextension region 158 joined to the lands 157 b, the conductive piece 9bonded to the extension region 158, and the conductive raised part 160 cto which the conductive piece 9 is bonded. The conductive piece 9functions as a relay terminal that electrically connects the sourceterminals 62 and the raised part 160 c.

The Zener diode 7 a is mounted to straddle between both the busbar 12and the wiring board 15 that is on the busbar 16, similarly to theMOSFETs 6 a. The insulating portion 142 is located between the busbar 12and the busbar 16. As shown in FIG. 21 , the Zener diode 7 a is providedon the busbars 12 and 16 so as to straddle the insulating portion 142.

The Zener diode 7 b is mounted to straddle between both the busbar 13and the wiring board 15 that is on the busbar 16, similarly to theMOSFETs 6 b. The insulating portion 143 is located between the busbar 13and the busbar 16. The Zener diode 7 b is provided on the busbars 13 and16 so as to straddle the insulating portion 143.

The cathode terminal 71 of the Zener diode 7 a is bonded to the uppersurface of the busbar 12 by the conductive bonding material 111,similarly to as described above. The cathode terminal 71 of the Zenerdiode 7 a is electrically connected to the drain terminals 63 of theMOSFETs 6 a through the busbar 12.

The cathode terminal 71 of the Zener diode 7 b is bonded to the uppersurface of the busbar 13 by the conductive bonding material 111,similarly to as described above. The cathode terminal 71 of the Zenerdiode 7 b is electrically connected to the drain terminals 63 of theMOSFETs 6 b through the busbar 13.

The anode terminal 72 of the Zener diode 7 a is bonded, similarly to asdescribed above, to the raised part 160 a in one of the two open holes152 a provided in the wiring board 15. The anode terminal 73 of theZener diode 7 a is bonded by the conductive bonding material 112,similarly to as described above, to the raised part 160 a in the otherof the two open holes 152 a. The anode terminal 72 of the Zener diode 7a is electrically connected to the source terminals 62 of the MOSFETs 6a through the raised part 160 a and the busbar 16.

The anode terminal 72 of the Zener diode 7 b is bonded, similarly to asdescribed above, to the raised part 160 b in one of the two open holes152 b provided in the wiring board 15. The anode terminal 73 of theZener diode 7 b is bonded by the conductive bonding material 112,similarly to as described above, to the raised part 160 b in the otherof the two open holes 152 b. The anode terminals 72 and 73 of the Zenerdiode 7 b is electrically connected to the source terminals 62 of theMOSFETs 6 b through the raised part 160 b and the busbar 16.

In the present example, given that the raised parts 160 a and 160 b areconstituted by part of the busbar 16, the anode terminals 72 and 73 canalso be said to be bonded to the upper surface of the busbar 16.

Example of Manufacturing Method for Circuit Structure

In the case of manufacturing the circuit structure 1B having aconfiguration such as the above, first, three pieces of theabove-described cladding material 10 (see FIG. 10 ) for producing thebusbars 12, 13 and 16 are prepared.

Next, cold forging, cutting or the like is performed on the three piecesof cladding material 10 to produce the busbars 12, 13 and 16, as shownin FIG. 25 .

Next, the busbars 12, 13 and 16 are disposed in a mold for insertmolding. A thermoplastic resin having excellent heat resistance such asPPS is then injected into the mold for insert molding from an injectionmolding machine, and the busbars 12, 13 and 16 and the resin are moldedas one piece. An integrally molded article in which the busbars 12, 13and 16 and the insulating member 14 are molded as one piece is therebyobtained.

Next, the wiring board 15 is fixed to the upper surface of the busbar 16included in the produced integrally molded article by a bonding materialsuch as double-sided adhesive tape. The structure shown in FIG. 24described above is thereby obtained.

Next, as shown in FIG. 26 , a solder paste 611 is applied topredetermined regions of the upper surfaces of the busbar 12, the busbar13, the busbar 16 and the wiring board 15. In FIG. 26 , the solder paste611 is shaded. The plurality of MOSFETs 6, the plurality of Zener diodes7, the plurality of connectors 8 and the plurality of conductive pieces9 are then soldered with a reflow method to the regions to which thesolder paste 611 was applied. The above-described circuit structure 1Bshown in FIGS. 17, 18 and other diagrams is thereby completed.

Thereafter, as shown in FIG. 27 , a heat sink 970 is attached to theback surfaces of the busbars 12, 13 and 16 via a heat conductive membersuch as a heat dissipation sheet. A case 980 covering the wiring board15, the plurality of MOSFETs 6, the plurality of Zener diodes 7, theplurality of connectors 8 and the plurality of conductive pieces 9 isthen attached to the busbars 12 and 13. An electrical junction box 990is thereby completed.

As described above, in the present example, given that the busbars 12and 13 are constituted by a cladding material, the linear expansioncoefficient of the busbars 12 and 13 as a whole can be approximated tothe linear expansion coefficient of the insulating member 14, togetherwith bonding of the drain terminals 63 to the busbars 12 and 13 beingfacilitated. Thermal stress is thereby less likely to occur in thebonding portion of the drain terminals 63 and the busbars 12 and 13,together with bonding of the drain terminals 63 to the busbars 12 and 13being facilitated. As a result, the reliability of the bonding portionimproves. Also, since heat generated by the MOSFETs 6 can be transferreddirectly to the busbars 12 and 13, local increases in temperature areless likely to occur. Similarly, thermal stress is less likely to occurin the bonding portion of the cathode terminals 71 and the busbars 12and 13, together with bonding of the cathode terminals 71 to the busbars12 and 13 being facilitated. As a result, the reliability of the bondingportion improves.

Also, in the present example, given that the busbar 16 is constituted bya cladding material, the linear expansion coefficient of the busbar 16as a whole can be approximated to the linear expansion coefficient ofthe insulating member 14, together with bonding of the anode terminals72 and 73 of the Zener diodes 7 to the busbar 16 (specifically, theraised parts 160 a and 160 b) being facilitated. Thermal stress isthereby less likely to occur in the bonding portion of the anodeterminals 72 and 73 and the busbar 16, together with bonding of theanode terminals 72 and 73 to the busbar 16 being facilitated. As aresult, the reliability of the bonding portion improves.

Also, in the present example, the busbars 12, 13 and 16 made of acladding material can be easily produced by laminating a plurality ofmetal layers, similarly to the busbars 2 and 3 described above. Also, inthe case where the metal layer that is used as the metal layer 260 bondsmore easily to the drain terminals 63 and the cathode terminal 71 thanthe metal layer 250, the linear expansion coefficient of the busbar 12as a whole can be approximated to the linear expansion coefficient ofthe insulating member 14, while at the same time facilitating bonding ofthe drain terminals 63 and the cathode terminal 71 to the metal layer260. Also, in the case where the metal layer that is used as the metallayer 360 bonds more easily to the drain terminals 63 and the cathodeterminal 71 than the metal layer 350, the linear expansion coefficientof the busbar 13 as a whole can be approximated to the linear expansioncoefficient of the insulating member 14, while at the same timefacilitating bonding of the drain terminals 63 and the cathode terminal71 to the metal layer 360.

Also, in the present example, the busbars 12, 13 and 16 made of acladding material can be easily produced using aluminum and copper,similarly to the busbars 2 and 3. Also, copper bonds more easily to thedrain terminals 63 and the cathode terminals 71 than aluminum, whereasaluminum has a linear expansion coefficient closer to the insulatingmember 14 than copper. Accordingly, the linear expansion coefficient ofthe busbar 12 as a whole can be approximated to the linear expansioncoefficient of the insulating member 14, while at the same timefacilitating bonding of the drain terminals 63 and the cathode terminal71 to the metal layer 260. Also, the linear expansion coefficient of thebusbar 13 as a whole can be approximated to the linear expansioncoefficient of the insulating member 14, while at the same timefacilitating bonding of the drain terminals 63 and the cathode terminal71 to the metal layer 360.

Also, in the busbar 12 according to the present example, given that thelinear expansion coefficient of the metal layer 250 is closer to thelinear expansion coefficient of the insulating member 14 than is thelinear expansion coefficient of the metal layer 260, a metal layerhaving a linear expansion coefficient close to the linear expansioncoefficient of the insulating member 14 can be employed as the metallayer 250, without considering bondability to the drain terminals 63 andthe cathode terminal 71. Similarly, a metal layer having a linearexpansion coefficient close to the linear expansion coefficient of theinsulating member 14 can be employed as the metal layer 350, withoutconsidering bondability to the drain terminals 63 and the cathodeterminal 71.

Also, in the present example, the upper end face of the insulatingportion 142 of the insulating member 14 is flush with the upper surfaceof the lower metal layer 250 having a linear expansion coefficient closeto the linear expansion coefficient of the insulating member 14 (e.g.,see FIG. 19 ). The upper metal layer 260 of the busbar 12 is therebyless likely to be affected by deformation of the insulating portion 142caused by changes in ambient temperature. As a result, thermal stress isless likely to occur in the bonding portion of the upper metal layer 260of the busbar 12 and the drain terminals 63 and cathode terminal 71.Accordingly, a metal layer having a large difference in linear expansioncoefficient from the insulating member 14 can be used as the metal layer260.

Also, in the present example, the upper end face of the insulatingportion 143 of the insulating member 14 is flush with the upper surfaceof the lower metal layer 350 having a linear expansion coefficient closeto the linear expansion coefficient of the insulating member 14 (e.g.,see FIG. 19 ). The upper metal layer 360 of the busbar 13 is therebyless likely to be affected by deformation of the insulating portion 143caused by changes in ambient temperature. As a result, thermal stress isless likely to occur in the bonding portion of the upper metal layer 360and the anode terminals 72 and 73. Accordingly, a metal layer having alarge difference in linear expansion coefficient from the insulatingmember 14 can be used as the metal layer 360.

Also, in the present example, the upper end faces of the insulatingportion 142 and the insulating portion 143 are flush with the uppersurface of the lower metal layer 250, the lower metal layer 650 and thelower metal layer 350, and the lower metal layer 250, the lower metallayer 650 and the lower metal layer 350 are constituted by the same typeof metal, such as aluminum, for example. The distribution of thermalstress in a direction along the upper surfaces of both the lower metallayer 250 and the lower metal layer 650 thus occurs symmetrically acrossthe insulating member 14 (left-right direction in FIG. 19 to FIG. 21 ),and the thermal stresses that occur on both sides cancel each other out.Similarly, the distribution of thermal stress in a direction along theupper surfaces of both the lower metal layer 650 and the lower metallayer 350 thus occurs symmetrically across the insulating member 14(left-right direction in FIG. 19 to FIG. 21 ), and the thermal stressesthat occur on both sides cancel each other out. As a result, thermalstress is less likely to occur in the bonding portions of the uppermetal layer 260 and the drain terminals 63 and cathode terminal 71(e.g., see FIG. 19 to FIG. 21 ), and the reliability of the bondingportions improves. Similarly, thermal stress is less likely to occur inthe bonding portions of the wiring board 15 on the upper metal layer 660and the gate terminals 61 and source terminals 62 (e.g., see FIGS. 19and 20 ), and the reliability of the bonding portions improves.Similarly, thermal stress is less likely to occur in the bondingportions of the upper metal layer 660 and the anode terminals 72 and 73(e.g., see FIG. 21 ), and the reliability of the bonding portionsimproves.

Also, in the present example, given that the busbar 12, the busbar 13,the busbar 16 and the insulating member 14 are molded as one piece, amember for integrating the busbar 12, the busbar 13, the busbar 16 andthe insulating member 14 is not required. The configuration of thecircuit structure 1B can thus be simplified.

Also, in the present example, the conductive raised parts 160 protrudefrom the busbar 16 into the open holes 152 of the wiring board 15. Byelectrically connecting the source terminals 62 on the wiring board 15to the raised parts 160 c in the open holes 152 c, the source terminals62 can thus be easily electrically connected to the busbar 16. Also, byelectrically connecting the anode terminals 72 and 73 on the wiringboard 15 to the raised parts 160 in the open holes 152, the anodeterminals 72 and 73 can be easily electrically connected to the busbar16.

In the present example, given that the raised parts 160 are constitutedby part of the busbar 16, electrical resistance between the sourceterminals 62 and the busbar 16 can be reduced, and also electricalresistance between the anode terminals 72 and 73 and the busbar 16 canbe reduced.

Also, in the present example, given that the anode terminals 72 and 73are bonded to the raised parts 160, electrical resistance between theanode terminals 72 and 73 and the busbar 16 can be reduced.

Also, in the present example, conductive pieces 9 bonded to theextension regions 158 that extend from the lands 157 a to which thesource terminals 62 of the MOSFETs 6 a are bonded and are located aroundthe open holes 152 c and to the upper surfaces of the raised parts 160 cin the open holes 152 c are provided. Due to such conductive pieces 9,electrical resistance between the source terminals 62 of the MOSFETs 6 aand the busbar 16 can be reduced. Also, given that transfer of heatgenerated by the MOSFETs 6 a to the busbar 16 is facilitated by theconductive pieces 9, local increases in temperature are less likely tooccur. Similarly, due to the conductive pieces 9, electrical resistancebetween the source terminals 62 of the MOSFETs 6 b and the busbar 16 canbe reduced. Also, given that transfer of heat generated by the MOSFETs 6b to the busbar 16 is facilitated by the conductive pieces 9, localincreases in temperature are less likely to occur.

Also, in the present example, the extension regions 158 surrounds theopen holes 152 c, and the conductive pieces 9 cover the opening edges ofthe open holes 152 c. The bonding area of the conductive pieces 9 andthe extension regions 158 and raised parts 160 c can thereby beincreased. As a result, electrical resistance between the sourceterminals 62 and the busbar 16 can be further reduced.

Also, in the present example, given that the wiring board 15 is locatedon a lower region than the upper surface of the busbars 12 and 13, onthe upper surface of the busbar 16, a difference in level between thewiring board 15 and the busbars 12 and 13 can be suppressed. Therefore,the MOSFETs 6 a and Zener diode 7 a can be easily provided to straddlebetween the wiring board 15 and the busbar 12. Also, the MOSFETs 6 b andthe Zener diode 7 b can be easily provided to straddle between thewiring board 15 and the busbar 13. In the present example, the entirearea of the upper surface of the busbar 16 is a lower region than theupper surface of the busbars 12 and 13, on the upper surface of thebusbar 16.

Also, in the present example, given that the extension regions 158 towhich the conductive pieces 9 are bonded extend from both the lands 157a to which the source terminals 62 of the MOSFETs 6 a are bonded and thelands 157 b to which the source terminals 62 of the MOSFETs 6 b arebonded and are located around the open holes 152 c, the extensionregions 158 can be shared by the MOSFETs 6 a and 6 b. Electricalresistance between the source terminals 62 and the busbar 16 of theMOSFETs 6 a and electrical resistance between the source terminals 62 ofthe MOSFETs 6 b and the busbar 16 can thereby be reduced with a simpleconfiguration.

Note that the linear expansion coefficient of the wiring board 15 iscloser to the linear expansion coefficient of the insulating member 14(e.g., 40 ppm/° C.) than are the linear expansion coefficients of theupper metal layers 260, 360 and 660 (e.g., 17 ppm/° C.). The linearexpansion coefficient of the wiring board 15 may, for example, be 18ppm/° C. or greater. Also, the linear expansion coefficient of thewiring board 15 may be closer to the linear expansion coefficient of theinsulating member 14 than are the linear expansion coefficients of thelower metal layers 250, 350 and 650 (e.g., 24 ppm/° C.). The linearexpansion coefficient of the wiring board may, for example, be 25 ppm/°C. or greater. Thermal stress is thereby less likely to occur in thebonding portion of the wiring board 15 and the source terminals 62. As aresult, the reliability of the bonding portion improves.

Also, the connection terminal of the wiring member extending from thebattery may be brought in contact with the upper metal layer 260 of theinput terminal part 121 of the busbar 12. Since the conductivity of theupper metal layer 260 is greater than the conductivity of the lowermetal layer 250, electrical resistance between the input terminal part121 and the battery can be reduced. Also, the connection terminal of thewiring member extending from an electrical component may be brought incontact with the upper metal layer 360 of the output terminal part 131of the busbar 13. Since the conductivity of the upper metal layer 360 isgreater than the conductivity of the lower metal layer 350, electricalresistance between the output terminal part 131 and the electricalcomponent can be reduced.

Other Examples of Circuit Structure

The structures of the circuit structures 1A and 1B are not limited tothe above examples. At least one of the busbars 2, 3, 12, 13 and 16 may,for example, be constituted by a cladding material consisting of threeor more metal layers. In this case, the uppermost metal layer may beconstituted by a material to which the connection terminals ofelectronic components are easily bonded by solder or the like. Theuppermost metal layer may, for example, be a copper layer.

Also, at least one of the busbars 2, 3, 12, 13 and 16 may be constitutedby a cladding material in which the end face of a metal layer and theend face of a metal layer are bonded. A cladding material in which, forexample, the end face of an aluminum layer and the end face of a copperlayer are diffusion bonded, rather than an aluminum layer and a copperlayer being laminated, may be employed for at least one of the busbars2, 3, 12, 13 and 16. In this case, the connection terminals ofelectronic components such as the MOSFETs 6 may be bonded to the copperlayer. Also, a cladding material in which three or more metal layers arearranged in one direction in the same plane and the end faces of twoadjacent metal layers are bonded together may be employed for at leastone of the busbars 2, 3, 12, 13 and 16.

The raised parts 302 may be constituted separately from the busbar 3,rather than being constituted by part of the busbar 3. In this case, theraised parts 302 may be bonded to the upper surface of the busbar 3 by aconductive bonding material such as solder. Similarly, the raised parts160 may be constituted separately from the busbar 16, rather than beingconstituted by part of the busbar 16. In this case, the raised parts 160may be bonded to the upper surface of the busbar 16 by a conductivebonding material such as solder.

Also, the circuit structure 1A may not include the wiring board 5. Inthis case, another busbar electrically insulated from the busbars 2 and3 by the insulating member 4 may be provided, for example. The sourceterminals 62 of the MOSFETs 6 may be bonded to the busbar 3, and thegate terminals 61 of the MOSFETs 6 may be bonded to the other busbar.

Similarly, the circuit structure 1B may not include the wiring board 15.In this case, another busbar electrically insulated from the busbars 12,13 and 16 by the insulating member 14 may be provided, for example. Thesource terminals 62 of the MOSFETs 6 may be bonded to the busbar 16, andthe gate terminals 61 of the MOSFETs 6 may be bonded to the otherbusbar.

Also, the circuit structure 1A may not include the conductive pieces 9.In this case, the raised part 302 in each open hole 52 and the extensionregion 533 around the open hole 52 may be bonded by solder or the like.Similarly, the circuit structure 1B may not include the conductivepieces 9. In this case, the raised part 160 in each open hole 152 andthe extension region 158 around the open hole 152 may be bonded bysolder or the like.

Also, in the circuit structure 1A, the upper end face of the surroundingportion 42 a included in the insulating portion 42 may be located lowerthan the upper surface of the lower metal layers 250 and 350, as shownin FIG. 28 . In this case, the upper metal layer 260 is, similarly, lesslikely to be affected by deformation of the insulating portion 42 causedby changes in ambient temperature. As a result, thermal stress is lesslikely to occur in the bonding portion of the upper metal layer 260 andthe drain terminals 63 and cathode terminal 71.

Similarly, in the circuit structure 1B, the upper end face of theinsulation portion 142 may be located lower than the upper surface ofthe lower metal layers 250, 350 and 650, as shown in FIG. 29 . Also, theupper end face of the insulating portion 143 may be located lower thanthe upper surface of the lower metal layers 250, 350 and 650.

Also, in the above example, the main body part 30 of the busbar 3includes the upper metal layer 360 in a portion other than the raisedparts 302, but may not include the upper metal layer 360 in a portionother than the raised parts 302. That is, in the main body part 30, onlythe plurality of raised parts 302 may be provided on the lower metallayer 350. In this case, the wiring board 5 is fixed on the lower metallayer 350 of the main body part 30. Similarly, in the busbar 16, onlythe plurality of raised parts 160 may be provided on the lower metallayer 650.

Also, the upper metal layers 260, 360 and 660 may be constituted by ametal material, other than copper, to which the drain terminals 63 andthe like are easily bonded by solder or the like. Also, the lower metallayers 250, 350 and 650 may be constituted by a metal material, otherthan aluminum, that has a linear expansion coefficient close to thelinear expansion coefficient of the insulating member 14. Also, theupper metal layers 260, 360 and 660 may have metal plating such asnickel plating on the surface thereof, in order to facilitate solderbonding of terminals or the like to the upper metal layers 260, 360 and660, to reduce contact resistance between wiring members and the inputterminal parts 21 and 121, and to reduce contact resistance betweenwiring members and the output terminal parts 31 and 131. In this case,the upper metal layers 60, 360 and 660 may be copper layers whosesurface has been metal plated.

Also, at least some of the busbars 2, 3, 12, 13 and 16 may beconstituted by different cladding materials. Also, at least one of thebusbars 2, 3, 12, 13 and 16 may not be a cladding material. For example,at least one of the busbars 2, 3, 12, 13 and 16 may be constituted byonly copper or may be constituted by only another type of metal.

Although a circuit structure has been described in detail above, theforegoing description is illustrative in all respects, and thedisclosure is not limited thereto. The various variations describedabove can be applied in combination as long as there are no mutualinconsistencies. Further, it should be understood that numerousvariations not illustrated herein can be contemplated without departingfrom the scope of the disclosure.

1. A circuit structure comprising: a first busbar; a wiring boardlocated on the first busbar and having an open hole; a conductive raisedpart protruding into the open hole from the first busbar; and a firstelectronic component having a first connection terminal, wherein thefirst connection terminal is electrically connected to the raised partin the open hole.
 2. The circuit structure according to claim 1, whereinthe raised part is constituted by part of the first busbar.
 3. Thecircuit structure according to claim 1, wherein the first connectionterminal is bonded to the raised part.
 4. The circuit structureaccording to claim 1, wherein the wiring board has: a first land towhich the first connection terminal is bonded; and a conductiveextension region extending from the first land and located around theopen hole, and the circuit structure further comprises a conductivepiece bonded to an upper surface of the raised part in the open hole andto the extension region.
 5. The circuit structure according to claim 4,wherein the extension region surrounds the open hole, and the conductivepiece covers an opening edge of the open hole.
 6. The circuit structureaccording to claim 4, further comprising: a second electronic componenthaving a second connection terminal located on the wiring board, whereinthe wiring board further has a second land to which the secondconnection terminal is bonded, and the extension region extends from thefirst land and the second land and is located around the open hole. 7.The circuit structure according to claim 1, further comprising: a secondbusbar, wherein the first electronic component is provided to straddlebetween the wiring board and the second busbar, and the wiring board islocated on a region, on an upper surface of the first busbar, lower thanan upper surface of the second busbar.
 8. The circuit structureaccording to claim 1, wherein the first busbar is constituted by acladding material.